AAPT2: Separate out the various steps

An early refactor. Some ideas became clearer as
development continued. Now the various phases are much
clearer and more easily reusable.

Also added a ton of tests!

Change-Id: Ic8f0a70c8222370352e63533b329c40457c0903e
diff --git a/tools/aapt2/compile/Compile.cpp b/tools/aapt2/compile/Compile.cpp
new file mode 100644
index 0000000..498bc9c
--- /dev/null
+++ b/tools/aapt2/compile/Compile.cpp
@@ -0,0 +1,419 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ConfigDescription.h"
+#include "Diagnostics.h"
+#include "Flags.h"
+#include "ResourceParser.h"
+#include "ResourceTable.h"
+#include "XmlDom.h"
+#include "XmlPullParser.h"
+
+#include "compile/IdAssigner.h"
+#include "compile/Png.h"
+#include "compile/XmlIdCollector.h"
+#include "flatten/FileExportWriter.h"
+#include "flatten/TableFlattener.h"
+#include "flatten/XmlFlattener.h"
+#include "util/Files.h"
+#include "util/Maybe.h"
+#include "util/Util.h"
+
+#include <fstream>
+#include <string>
+
+namespace aapt {
+
+struct ResourcePathData {
+    Source source;
+    std::u16string resourceDir;
+    std::u16string name;
+    std::string extension;
+
+    // Original config str. We keep this because when we parse the config, we may add on
+    // version qualifiers. We want to preserve the original input so the output is easily
+    // computed before hand.
+    std::string configStr;
+    ConfigDescription config;
+};
+
+/**
+ * Resource file paths are expected to look like:
+ * [--/res/]type[-config]/name
+ */
+static Maybe<ResourcePathData> extractResourcePathData(const std::string& path,
+                                                       std::string* outError) {
+    std::vector<std::string> parts = util::split(path, file::sDirSep);
+    if (parts.size() < 2) {
+        if (outError) *outError = "bad resource path";
+        return {};
+    }
+
+    std::string& dir = parts[parts.size() - 2];
+    StringPiece dirStr = dir;
+
+    StringPiece configStr;
+    ConfigDescription config;
+    size_t dashPos = dir.find('-');
+    if (dashPos != std::string::npos) {
+        configStr = dirStr.substr(dashPos + 1, dir.size() - (dashPos + 1));
+        if (!ConfigDescription::parse(configStr, &config)) {
+            if (outError) {
+                std::stringstream errStr;
+                errStr << "invalid configuration '" << configStr << "'";
+                *outError = errStr.str();
+            }
+            return {};
+        }
+        dirStr = dirStr.substr(0, dashPos);
+    }
+
+    std::string& filename = parts[parts.size() - 1];
+    StringPiece name = filename;
+    StringPiece extension;
+    size_t dotPos = filename.find('.');
+    if (dotPos != std::string::npos) {
+        extension = name.substr(dotPos + 1, filename.size() - (dotPos + 1));
+        name = name.substr(0, dotPos);
+    }
+
+    return ResourcePathData{
+            Source{ path },
+            util::utf8ToUtf16(dirStr),
+            util::utf8ToUtf16(name),
+            extension.toString(),
+            configStr.toString(),
+            config
+    };
+}
+
+struct CompileOptions {
+    std::string outputPath;
+    bool verbose = false;
+};
+
+static std::string buildIntermediateFilename(const std::string outDir,
+                                             const ResourcePathData& data) {
+    std::stringstream name;
+    name << data.resourceDir;
+    if (!data.configStr.empty()) {
+        name << "-" << data.configStr;
+    }
+    name << "_" << data.name << "." << data.extension << ".flat";
+    std::string outPath = outDir;
+    file::appendPath(&outPath, name.str());
+    return outPath;
+}
+
+static bool compileTable(IAaptContext* context, const CompileOptions& options,
+                         const ResourcePathData& pathData, const std::string& outputPath) {
+    ResourceTable table;
+    table.createPackage(u"", 0x7f);
+
+    {
+        std::ifstream fin(pathData.source.path, std::ifstream::binary);
+        if (!fin) {
+            context->getDiagnostics()->error(DiagMessage(pathData.source) << strerror(errno));
+            return false;
+        }
+
+
+        // Parse the values file from XML.
+        XmlPullParser xmlParser(fin);
+        ResourceParser resParser(context->getDiagnostics(), &table, pathData.source,
+                                 pathData.config);
+        if (!resParser.parse(&xmlParser)) {
+            return false;
+        }
+
+        fin.close();
+    }
+
+    // Assign IDs to prepare the table for flattening.
+    IdAssigner idAssigner;
+    if (!idAssigner.consume(context, &table)) {
+        return false;
+    }
+
+    // Flatten the table.
+    BigBuffer buffer(1024);
+    TableFlattenerOptions tableFlattenerOptions;
+    tableFlattenerOptions.useExtendedChunks = true;
+    TableFlattener flattener(&buffer, tableFlattenerOptions);
+    if (!flattener.consume(context, &table)) {
+        return false;
+    }
+
+    // Build the output filename.
+    std::ofstream fout(outputPath, std::ofstream::binary);
+    if (!fout) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+
+    // Write it to disk.
+    if (!util::writeAll(fout, buffer)) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+    return true;
+}
+
+static bool compileXml(IAaptContext* context, const CompileOptions& options,
+                       const ResourcePathData& pathData, const std::string& outputPath) {
+
+    std::unique_ptr<XmlResource> xmlRes;
+
+    {
+        std::ifstream fin(pathData.source.path, std::ifstream::binary);
+        if (!fin) {
+            context->getDiagnostics()->error(DiagMessage(pathData.source) << strerror(errno));
+            return false;
+        }
+
+        xmlRes = xml::inflate(&fin, context->getDiagnostics(), pathData.source);
+
+        fin.close();
+    }
+
+    if (!xmlRes) {
+        return false;
+    }
+
+    // Collect IDs that are defined here.
+    XmlIdCollector collector;
+    if (!collector.consume(context, xmlRes.get())) {
+        return false;
+    }
+
+    xmlRes->file.name = ResourceName{ {}, *parseResourceType(pathData.resourceDir), pathData.name };
+    xmlRes->file.config = pathData.config;
+    xmlRes->file.source = pathData.source;
+
+    BigBuffer buffer(1024);
+    ChunkWriter fileExportWriter = wrapBufferWithFileExportHeader(&buffer, &xmlRes->file);
+
+    XmlFlattenerOptions xmlFlattenerOptions;
+    xmlFlattenerOptions.keepRawValues = true;
+    XmlFlattener flattener(fileExportWriter.getBuffer(), xmlFlattenerOptions);
+    if (!flattener.consume(context, xmlRes.get())) {
+        return false;
+    }
+
+    fileExportWriter.finish();
+
+    std::ofstream fout(outputPath, std::ofstream::binary);
+    if (!fout) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+
+    // Write it to disk.
+    if (!util::writeAll(fout, buffer)) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+    return true;
+}
+
+static bool compilePng(IAaptContext* context, const CompileOptions& options,
+                       const ResourcePathData& pathData, const std::string& outputPath) {
+    BigBuffer buffer(4096);
+    ResourceFile resFile;
+    resFile.name = ResourceName{ {}, *parseResourceType(pathData.resourceDir), pathData.name };
+    resFile.config = pathData.config;
+    resFile.source = pathData.source;
+
+    ChunkWriter fileExportWriter = wrapBufferWithFileExportHeader(&buffer, &resFile);
+
+    {
+        std::ifstream fin(pathData.source.path, std::ifstream::binary);
+        if (!fin) {
+            context->getDiagnostics()->error(DiagMessage(pathData.source) << strerror(errno));
+            return false;
+        }
+
+        Png png(context->getDiagnostics());
+        if (!png.process(pathData.source, &fin, fileExportWriter.getBuffer(), {})) {
+            return false;
+        }
+    }
+
+    fileExportWriter.finish();
+
+    std::ofstream fout(outputPath, std::ofstream::binary);
+    if (!fout) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+
+    if (!util::writeAll(fout, buffer)) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+    return true;
+}
+
+static bool compileFile(IAaptContext* context, const CompileOptions& options,
+                        const ResourcePathData& pathData, const std::string& outputPath) {
+    BigBuffer buffer(256);
+    ResourceFile resFile;
+    resFile.name = ResourceName{ {}, *parseResourceType(pathData.resourceDir), pathData.name };
+    resFile.config = pathData.config;
+    resFile.source = pathData.source;
+
+    ChunkWriter fileExportWriter = wrapBufferWithFileExportHeader(&buffer, &resFile);
+
+    std::string errorStr;
+    Maybe<android::FileMap> f = file::mmapPath(pathData.source.path, &errorStr);
+    if (!f) {
+        context->getDiagnostics()->error(DiagMessage(pathData.source) << errorStr);
+        return false;
+    }
+
+    std::ofstream fout(outputPath, std::ofstream::binary);
+    if (!fout) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+
+    // Manually set the size and don't call finish(). This is because we are not copying from
+    // the buffer the entire file.
+    fileExportWriter.getChunkHeader()->size =
+            util::hostToDevice32(buffer.size() + f.value().getDataLength());
+    if (!util::writeAll(fout, buffer)) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+
+    if (!fout.write((const char*) f.value().getDataPtr(), f.value().getDataLength())) {
+        context->getDiagnostics()->error(DiagMessage(Source{ outputPath }) << strerror(errno));
+        return false;
+    }
+    return true;
+}
+
+class CompileContext : public IAaptContext {
+private:
+    StdErrDiagnostics mDiagnostics;
+
+public:
+    IDiagnostics* getDiagnostics() override {
+       return &mDiagnostics;
+    }
+
+    NameMangler* getNameMangler() override {
+       abort();
+       return nullptr;
+    }
+
+    StringPiece16 getCompilationPackage() override {
+       return {};
+    }
+
+    uint8_t getPackageId() override {
+       return 0x7f;
+    }
+
+    ISymbolTable* getExternalSymbols() override {
+       abort();
+       return nullptr;
+    }
+};
+
+/**
+ * Entry point for compilation phase. Parses arguments and dispatches to the correct steps.
+ */
+int compile(const std::vector<StringPiece>& args) {
+    CompileOptions options;
+
+    Flags flags = Flags()
+            .requiredFlag("-o", "Output path", &options.outputPath)
+            .optionalSwitch("-v", "Enables verbose logging", &options.verbose);
+    if (!flags.parse("aapt2 compile", args, &std::cerr)) {
+        return 1;
+    }
+
+    CompileContext context;
+
+    std::vector<ResourcePathData> inputData;
+    inputData.reserve(flags.getArgs().size());
+
+    // Collect data from the path for each input file.
+    for (const std::string& arg : flags.getArgs()) {
+        std::string errorStr;
+        if (Maybe<ResourcePathData> pathData = extractResourcePathData(arg, &errorStr)) {
+            inputData.push_back(std::move(pathData.value()));
+        } else {
+            context.getDiagnostics()->error(DiagMessage() << errorStr << " (" << arg << ")");
+            return 1;
+        }
+    }
+
+    bool error = false;
+    for (ResourcePathData& pathData : inputData) {
+        if (options.verbose) {
+            context.getDiagnostics()->note(DiagMessage(pathData.source) << "processing");
+        }
+
+        if (pathData.resourceDir == u"values") {
+            // Overwrite the extension.
+            pathData.extension = "arsc";
+
+            const std::string outputFilename = buildIntermediateFilename(
+                    options.outputPath, pathData);
+            if (!compileTable(&context, options, pathData, outputFilename)) {
+                error = true;
+            }
+
+        } else {
+            const std::string outputFilename = buildIntermediateFilename(options.outputPath,
+                                                                         pathData);
+            if (const ResourceType* type = parseResourceType(pathData.resourceDir)) {
+                if (*type != ResourceType::kRaw) {
+                    if (pathData.extension == "xml") {
+                        if (!compileXml(&context, options, pathData, outputFilename)) {
+                            error = true;
+                        }
+                    } else if (pathData.extension == "png" || pathData.extension == "9.png") {
+                        if (!compilePng(&context, options, pathData, outputFilename)) {
+                            error = true;
+                        }
+                    } else {
+                        if (!compileFile(&context, options, pathData, outputFilename)) {
+                            error = true;
+                        }
+                    }
+                } else {
+                    if (!compileFile(&context, options, pathData, outputFilename)) {
+                        error = true;
+                    }
+                }
+            } else {
+                context.getDiagnostics()->error(
+                        DiagMessage() << "invalid file path '" << pathData.source << "'");
+                error = true;
+            }
+        }
+    }
+
+    if (error) {
+        return 1;
+    }
+    return 0;
+}
+
+} // namespace aapt
diff --git a/tools/aapt2/compile/IdAssigner.cpp b/tools/aapt2/compile/IdAssigner.cpp
new file mode 100644
index 0000000..80c6bbc
--- /dev/null
+++ b/tools/aapt2/compile/IdAssigner.cpp
@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ResourceTable.h"
+
+#include "compile/IdAssigner.h"
+#include "process/IResourceTableConsumer.h"
+#include "util/Util.h"
+
+#include <bitset>
+#include <cassert>
+#include <set>
+
+namespace aapt {
+
+bool IdAssigner::consume(IAaptContext* context, ResourceTable* table) {
+    std::bitset<256> usedTypeIds;
+    std::set<uint16_t> usedEntryIds;
+
+    for (auto& package : table->packages) {
+        assert(package->id && "packages must have manually assigned IDs");
+
+        usedTypeIds.reset();
+
+        // Type ID 0 is invalid, reserve it.
+        usedTypeIds.set(0);
+
+        // Collect used type IDs.
+        for (auto& type : package->types) {
+            if (type->id) {
+                usedEntryIds.clear();
+
+                if (usedTypeIds[type->id.value()]) {
+                    // This ID is already taken!
+                    context->getDiagnostics()->error(DiagMessage()
+                                                     << "type '" << type->type << "' in "
+                                                     << "package '" << package->name << "' has "
+                                                     << "duplicate ID "
+                                                     << std::hex << (int) type->id.value()
+                                                     << std::dec);
+                    return false;
+                }
+
+                // Mark the type ID as taken.
+                usedTypeIds.set(type->id.value());
+            }
+
+            // Collect used entry IDs.
+            for (auto& entry : type->entries) {
+                if (entry->id) {
+                    // Mark entry ID as taken.
+                    if (!usedEntryIds.insert(entry->id.value()).second) {
+                        // This ID existed before!
+                        ResourceNameRef nameRef =
+                                { package->name, type->type, entry->name };
+                        ResourceId takenId(package->id.value(), type->id.value(),
+                                           entry->id.value());
+                        context->getDiagnostics()->error(DiagMessage()
+                                                         << "resource '" << nameRef << "' "
+                                                         << "has duplicate ID '"
+                                                         << takenId << "'");
+                        return false;
+                    }
+                }
+            }
+
+            // Assign unused entry IDs.
+            const auto endUsedEntryIter = usedEntryIds.end();
+            auto nextUsedEntryIter = usedEntryIds.begin();
+            uint16_t nextId = 0;
+            for (auto& entry : type->entries) {
+                if (!entry->id) {
+                    // Assign the next available entryID.
+                    while (nextUsedEntryIter != endUsedEntryIter &&
+                            nextId == *nextUsedEntryIter) {
+                        nextId++;
+                        ++nextUsedEntryIter;
+                    }
+                    entry->id = nextId++;
+                }
+            }
+        }
+
+        // Assign unused type IDs.
+        size_t nextTypeId = 0;
+        for (auto& type : package->types) {
+            if (!type->id) {
+                while (nextTypeId < usedTypeIds.size() && usedTypeIds[nextTypeId]) {
+                    nextTypeId++;
+                }
+                type->id = static_cast<uint8_t>(nextTypeId);
+                nextTypeId++;
+            }
+        }
+    }
+    return true;
+}
+
+} // namespace aapt
diff --git a/tools/aapt2/compile/IdAssigner.h b/tools/aapt2/compile/IdAssigner.h
new file mode 100644
index 0000000..514df3a
--- /dev/null
+++ b/tools/aapt2/compile/IdAssigner.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef AAPT_COMPILE_IDASSIGNER_H
+#define AAPT_COMPILE_IDASSIGNER_H
+
+#include "process/IResourceTableConsumer.h"
+
+namespace aapt {
+
+/**
+ * Assigns IDs to each resource in the table, respecting existing IDs and filling in gaps
+ * in between fixed ID assignments.
+ */
+struct IdAssigner : public IResourceTableConsumer {
+    bool consume(IAaptContext* context, ResourceTable* table) override;
+};
+
+} // namespace aapt
+
+#endif /* AAPT_COMPILE_IDASSIGNER_H */
diff --git a/tools/aapt2/compile/IdAssigner_test.cpp b/tools/aapt2/compile/IdAssigner_test.cpp
new file mode 100644
index 0000000..e25a17a
--- /dev/null
+++ b/tools/aapt2/compile/IdAssigner_test.cpp
@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "compile/IdAssigner.h"
+
+#include "test/Context.h"
+#include "test/Builders.h"
+
+#include <gtest/gtest.h>
+
+namespace aapt {
+
+::testing::AssertionResult verifyIds(ResourceTable* table);
+
+TEST(IdAssignerTest, AssignIds) {
+    std::unique_ptr<ResourceTable> table = test::ResourceTableBuilder()
+            .addSimple(u"@android:attr/foo")
+            .addSimple(u"@android:attr/bar")
+            .addSimple(u"@android:id/foo")
+            .setPackageId(u"android", 0x01)
+            .build();
+
+    std::unique_ptr<IAaptContext> context = test::ContextBuilder().build();
+    IdAssigner assigner;
+
+    ASSERT_TRUE(assigner.consume(context.get(), table.get()));
+    ASSERT_TRUE(verifyIds(table.get()));
+}
+
+TEST(IdAssignerTest, AssignIdsWithReservedIds) {
+    std::unique_ptr<ResourceTable> table = test::ResourceTableBuilder()
+            .addSimple(u"@android:attr/foo", ResourceId(0x01040006))
+            .addSimple(u"@android:attr/bar")
+            .addSimple(u"@android:id/foo")
+            .addSimple(u"@app:id/biz")
+            .setPackageId(u"android", 0x01)
+            .setPackageId(u"app", 0x7f)
+            .build();
+
+    std::unique_ptr<IAaptContext> context = test::ContextBuilder().build();
+    IdAssigner assigner;
+
+    ASSERT_TRUE(assigner.consume(context.get(), table.get()));
+    ASSERT_TRUE(verifyIds(table.get()));
+}
+
+TEST(IdAssignerTest, FailWhenNonUniqueIdsAssigned) {
+    std::unique_ptr<ResourceTable> table = test::ResourceTableBuilder()
+            .addSimple(u"@android:attr/foo", ResourceId(0x01040006))
+            .addSimple(u"@android:attr/bar", ResourceId(0x01040006))
+            .setPackageId(u"android", 0x01)
+            .setPackageId(u"app", 0x7f)
+            .build();
+
+    std::unique_ptr<IAaptContext> context = test::ContextBuilder().build();
+    IdAssigner assigner;
+
+    ASSERT_FALSE(assigner.consume(context.get(), table.get()));
+}
+
+::testing::AssertionResult verifyIds(ResourceTable* table) {
+    std::set<uint8_t> packageIds;
+    for (auto& package : table->packages) {
+        if (!package->id) {
+            return ::testing::AssertionFailure() << "package " << package->name << " has no ID";
+        }
+
+        if (!packageIds.insert(package->id.value()).second) {
+            return ::testing::AssertionFailure() << "package " << package->name
+                    << " has non-unique ID " << std::hex << (int) package->id.value() << std::dec;
+        }
+    }
+
+    for (auto& package : table->packages) {
+        std::set<uint8_t> typeIds;
+        for (auto& type : package->types) {
+            if (!type->id) {
+                return ::testing::AssertionFailure() << "type " << type->type << " of package "
+                        << package->name << " has no ID";
+            }
+
+            if (!typeIds.insert(type->id.value()).second) {
+                return ::testing::AssertionFailure() << "type " << type->type
+                        << " of package " << package->name << " has non-unique ID "
+                        << std::hex << (int) type->id.value() << std::dec;
+            }
+        }
+
+
+        for (auto& type : package->types) {
+            std::set<uint16_t> entryIds;
+            for (auto& entry : type->entries) {
+                if (!entry->id) {
+                    return ::testing::AssertionFailure() << "entry " << entry->name << " of type "
+                            << type->type << " of package " << package->name << " has no ID";
+                }
+
+                if (!entryIds.insert(entry->id.value()).second) {
+                    return ::testing::AssertionFailure() << "entry " << entry->name
+                            << " of type " << type->type << " of package " << package->name
+                            << " has non-unique ID "
+                            << std::hex << (int) entry->id.value() << std::dec;
+                }
+            }
+        }
+    }
+    return ::testing::AssertionSuccess() << "all IDs are unique and assigned";
+}
+
+} // namespace aapt
diff --git a/tools/aapt2/compile/Png.cpp b/tools/aapt2/compile/Png.cpp
new file mode 100644
index 0000000..9837c4e
--- /dev/null
+++ b/tools/aapt2/compile/Png.cpp
@@ -0,0 +1,1278 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "util/BigBuffer.h"
+#include "Png.h"
+#include "Source.h"
+#include "util/Util.h"
+
+#include <androidfw/ResourceTypes.h>
+#include <iostream>
+#include <png.h>
+#include <sstream>
+#include <string>
+#include <vector>
+#include <zlib.h>
+
+namespace aapt {
+
+constexpr bool kDebug = false;
+constexpr size_t kPngSignatureSize = 8u;
+
+struct PngInfo {
+    ~PngInfo() {
+        for (png_bytep row : rows) {
+            if (row != nullptr) {
+                delete[] row;
+            }
+        }
+
+        delete[] xDivs;
+        delete[] yDivs;
+    }
+
+    void* serialize9Patch() {
+        void* serialized = android::Res_png_9patch::serialize(info9Patch, xDivs, yDivs,
+                                                              colors.data());
+        reinterpret_cast<android::Res_png_9patch*>(serialized)->deviceToFile();
+        return serialized;
+    }
+
+    uint32_t width = 0;
+    uint32_t height = 0;
+    std::vector<png_bytep> rows;
+
+    bool is9Patch = false;
+    android::Res_png_9patch info9Patch;
+    int32_t* xDivs = nullptr;
+    int32_t* yDivs = nullptr;
+    std::vector<uint32_t> colors;
+
+    // Layout padding.
+    bool haveLayoutBounds = false;
+    int32_t layoutBoundsLeft;
+    int32_t layoutBoundsTop;
+    int32_t layoutBoundsRight;
+    int32_t layoutBoundsBottom;
+
+    // Round rect outline description.
+    int32_t outlineInsetsLeft;
+    int32_t outlineInsetsTop;
+    int32_t outlineInsetsRight;
+    int32_t outlineInsetsBottom;
+    float outlineRadius;
+    uint8_t outlineAlpha;
+};
+
+static void readDataFromStream(png_structp readPtr, png_bytep data, png_size_t length) {
+    std::istream* input = reinterpret_cast<std::istream*>(png_get_io_ptr(readPtr));
+    if (!input->read(reinterpret_cast<char*>(data), length)) {
+        png_error(readPtr, strerror(errno));
+    }
+}
+
+static void writeDataToStream(png_structp writePtr, png_bytep data, png_size_t length) {
+    BigBuffer* outBuffer = reinterpret_cast<BigBuffer*>(png_get_io_ptr(writePtr));
+    png_bytep buf = outBuffer->nextBlock<png_byte>(length);
+    memcpy(buf, data, length);
+}
+
+static void flushDataToStream(png_structp /*writePtr*/) {
+}
+
+static void logWarning(png_structp readPtr, png_const_charp warningMessage) {
+    IDiagnostics* diag = reinterpret_cast<IDiagnostics*>(png_get_error_ptr(readPtr));
+    diag->warn(DiagMessage() << warningMessage);
+}
+
+
+static bool readPng(IDiagnostics* diag, png_structp readPtr, png_infop infoPtr, PngInfo* outInfo) {
+    if (setjmp(png_jmpbuf(readPtr))) {
+        diag->error(DiagMessage() << "failed reading png");
+        return false;
+    }
+
+    png_set_sig_bytes(readPtr, kPngSignatureSize);
+    png_read_info(readPtr, infoPtr);
+
+    int colorType, bitDepth, interlaceType, compressionType;
+    png_get_IHDR(readPtr, infoPtr, &outInfo->width, &outInfo->height, &bitDepth, &colorType,
+                 &interlaceType, &compressionType, nullptr);
+
+    if (colorType == PNG_COLOR_TYPE_PALETTE) {
+        png_set_palette_to_rgb(readPtr);
+    }
+
+    if (colorType == PNG_COLOR_TYPE_GRAY && bitDepth < 8) {
+        png_set_expand_gray_1_2_4_to_8(readPtr);
+    }
+
+    if (png_get_valid(readPtr, infoPtr, PNG_INFO_tRNS)) {
+        png_set_tRNS_to_alpha(readPtr);
+    }
+
+    if (bitDepth == 16) {
+        png_set_strip_16(readPtr);
+    }
+
+    if (!(colorType & PNG_COLOR_MASK_ALPHA)) {
+        png_set_add_alpha(readPtr, 0xFF, PNG_FILLER_AFTER);
+    }
+
+    if (colorType == PNG_COLOR_TYPE_GRAY || colorType == PNG_COLOR_TYPE_GRAY_ALPHA) {
+        png_set_gray_to_rgb(readPtr);
+    }
+
+    png_set_interlace_handling(readPtr);
+    png_read_update_info(readPtr, infoPtr);
+
+    const uint32_t rowBytes = png_get_rowbytes(readPtr, infoPtr);
+    outInfo->rows.resize(outInfo->height);
+    for (size_t i = 0; i < outInfo->height; i++) {
+        outInfo->rows[i] = new png_byte[rowBytes];
+    }
+
+    png_read_image(readPtr, outInfo->rows.data());
+    png_read_end(readPtr, infoPtr);
+    return true;
+}
+
+static void checkNinePatchSerialization(android::Res_png_9patch* inPatch,  void* data) {
+    size_t patchSize = inPatch->serializedSize();
+    void* newData = malloc(patchSize);
+    memcpy(newData, data, patchSize);
+    android::Res_png_9patch* outPatch = inPatch->deserialize(newData);
+    outPatch->fileToDevice();
+    // deserialization is done in place, so outPatch == newData
+    assert(outPatch == newData);
+    assert(outPatch->numXDivs == inPatch->numXDivs);
+    assert(outPatch->numYDivs == inPatch->numYDivs);
+    assert(outPatch->paddingLeft == inPatch->paddingLeft);
+    assert(outPatch->paddingRight == inPatch->paddingRight);
+    assert(outPatch->paddingTop == inPatch->paddingTop);
+    assert(outPatch->paddingBottom == inPatch->paddingBottom);
+/*    for (int i = 0; i < outPatch->numXDivs; i++) {
+        assert(outPatch->getXDivs()[i] == inPatch->getXDivs()[i]);
+    }
+    for (int i = 0; i < outPatch->numYDivs; i++) {
+        assert(outPatch->getYDivs()[i] == inPatch->getYDivs()[i]);
+    }
+    for (int i = 0; i < outPatch->numColors; i++) {
+        assert(outPatch->getColors()[i] == inPatch->getColors()[i]);
+    }*/
+    free(newData);
+}
+
+/*static void dump_image(int w, int h, const png_byte* const* rows, int color_type) {
+    int i, j, rr, gg, bb, aa;
+
+    int bpp;
+    if (color_type == PNG_COLOR_TYPE_PALETTE || color_type == PNG_COLOR_TYPE_GRAY) {
+        bpp = 1;
+    } else if (color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
+        bpp = 2;
+    } else if (color_type == PNG_COLOR_TYPE_RGB || color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
+        // We use a padding byte even when there is no alpha
+        bpp = 4;
+    } else {
+        printf("Unknown color type %d.\n", color_type);
+    }
+
+    for (j = 0; j < h; j++) {
+        const png_byte* row = rows[j];
+        for (i = 0; i < w; i++) {
+            rr = row[0];
+            gg = row[1];
+            bb = row[2];
+            aa = row[3];
+            row += bpp;
+
+            if (i == 0) {
+                printf("Row %d:", j);
+            }
+            switch (bpp) {
+            case 1:
+                printf(" (%d)", rr);
+                break;
+            case 2:
+                printf(" (%d %d", rr, gg);
+                break;
+            case 3:
+                printf(" (%d %d %d)", rr, gg, bb);
+                break;
+            case 4:
+                printf(" (%d %d %d %d)", rr, gg, bb, aa);
+                break;
+            }
+            if (i == (w - 1)) {
+                printf("\n");
+            }
+        }
+    }
+}*/
+
+#define MAX(a,b) ((a)>(b)?(a):(b))
+#define ABS(a)   ((a)<0?-(a):(a))
+
+static void analyze_image(IDiagnostics* diag, const PngInfo& imageInfo, int grayscaleTolerance,
+                          png_colorp rgbPalette, png_bytep alphaPalette,
+                          int *paletteEntries, bool *hasTransparency, int *colorType,
+                          png_bytepp outRows) {
+    int w = imageInfo.width;
+    int h = imageInfo.height;
+    int i, j, rr, gg, bb, aa, idx;
+    uint32_t colors[256], col;
+    int num_colors = 0;
+    int maxGrayDeviation = 0;
+
+    bool isOpaque = true;
+    bool isPalette = true;
+    bool isGrayscale = true;
+
+    // Scan the entire image and determine if:
+    // 1. Every pixel has R == G == B (grayscale)
+    // 2. Every pixel has A == 255 (opaque)
+    // 3. There are no more than 256 distinct RGBA colors
+
+    if (kDebug) {
+        printf("Initial image data:\n");
+        //dump_image(w, h, imageInfo.rows.data(), PNG_COLOR_TYPE_RGB_ALPHA);
+    }
+
+    for (j = 0; j < h; j++) {
+        const png_byte* row = imageInfo.rows[j];
+        png_bytep out = outRows[j];
+        for (i = 0; i < w; i++) {
+            rr = *row++;
+            gg = *row++;
+            bb = *row++;
+            aa = *row++;
+
+            int odev = maxGrayDeviation;
+            maxGrayDeviation = MAX(ABS(rr - gg), maxGrayDeviation);
+            maxGrayDeviation = MAX(ABS(gg - bb), maxGrayDeviation);
+            maxGrayDeviation = MAX(ABS(bb - rr), maxGrayDeviation);
+            if (maxGrayDeviation > odev) {
+                if (kDebug) {
+                    printf("New max dev. = %d at pixel (%d, %d) = (%d %d %d %d)\n",
+                            maxGrayDeviation, i, j, rr, gg, bb, aa);
+                }
+            }
+
+            // Check if image is really grayscale
+            if (isGrayscale) {
+                if (rr != gg || rr != bb) {
+                    if (kDebug) {
+                        printf("Found a non-gray pixel at %d, %d = (%d %d %d %d)\n",
+                                i, j, rr, gg, bb, aa);
+                    }
+                    isGrayscale = false;
+                }
+            }
+
+            // Check if image is really opaque
+            if (isOpaque) {
+                if (aa != 0xff) {
+                    if (kDebug) {
+                        printf("Found a non-opaque pixel at %d, %d = (%d %d %d %d)\n",
+                                i, j, rr, gg, bb, aa);
+                    }
+                    isOpaque = false;
+                }
+            }
+
+            // Check if image is really <= 256 colors
+            if (isPalette) {
+                col = (uint32_t) ((rr << 24) | (gg << 16) | (bb << 8) | aa);
+                bool match = false;
+                for (idx = 0; idx < num_colors; idx++) {
+                    if (colors[idx] == col) {
+                        match = true;
+                        break;
+                    }
+                }
+
+                // Write the palette index for the pixel to outRows optimistically
+                // We might overwrite it later if we decide to encode as gray or
+                // gray + alpha
+                *out++ = idx;
+                if (!match) {
+                    if (num_colors == 256) {
+                        if (kDebug) {
+                            printf("Found 257th color at %d, %d\n", i, j);
+                        }
+                        isPalette = false;
+                    } else {
+                        colors[num_colors++] = col;
+                    }
+                }
+            }
+        }
+    }
+
+    *paletteEntries = 0;
+    *hasTransparency = !isOpaque;
+    int bpp = isOpaque ? 3 : 4;
+    int paletteSize = w * h + bpp * num_colors;
+
+    if (kDebug) {
+        printf("isGrayscale = %s\n", isGrayscale ? "true" : "false");
+        printf("isOpaque = %s\n", isOpaque ? "true" : "false");
+        printf("isPalette = %s\n", isPalette ? "true" : "false");
+        printf("Size w/ palette = %d, gray+alpha = %d, rgb(a) = %d\n",
+                paletteSize, 2 * w * h, bpp * w * h);
+        printf("Max gray deviation = %d, tolerance = %d\n", maxGrayDeviation, grayscaleTolerance);
+    }
+
+    // Choose the best color type for the image.
+    // 1. Opaque gray - use COLOR_TYPE_GRAY at 1 byte/pixel
+    // 2. Gray + alpha - use COLOR_TYPE_PALETTE if the number of distinct combinations
+    //     is sufficiently small, otherwise use COLOR_TYPE_GRAY_ALPHA
+    // 3. RGB(A) - use COLOR_TYPE_PALETTE if the number of distinct colors is sufficiently
+    //     small, otherwise use COLOR_TYPE_RGB{_ALPHA}
+    if (isGrayscale) {
+        if (isOpaque) {
+            *colorType = PNG_COLOR_TYPE_GRAY; // 1 byte/pixel
+        } else {
+            // Use a simple heuristic to determine whether using a palette will
+            // save space versus using gray + alpha for each pixel.
+            // This doesn't take into account chunk overhead, filtering, LZ
+            // compression, etc.
+            if (isPalette && (paletteSize < 2 * w * h)) {
+                *colorType = PNG_COLOR_TYPE_PALETTE; // 1 byte/pixel + 4 bytes/color
+            } else {
+                *colorType = PNG_COLOR_TYPE_GRAY_ALPHA; // 2 bytes per pixel
+            }
+        }
+    } else if (isPalette && (paletteSize < bpp * w * h)) {
+        *colorType = PNG_COLOR_TYPE_PALETTE;
+    } else {
+        if (maxGrayDeviation <= grayscaleTolerance) {
+            diag->note(DiagMessage()
+                       << "forcing image to gray (max deviation = "
+                       << maxGrayDeviation << ")");
+            *colorType = isOpaque ? PNG_COLOR_TYPE_GRAY : PNG_COLOR_TYPE_GRAY_ALPHA;
+        } else {
+            *colorType = isOpaque ? PNG_COLOR_TYPE_RGB : PNG_COLOR_TYPE_RGB_ALPHA;
+        }
+    }
+
+    // Perform postprocessing of the image or palette data based on the final
+    // color type chosen
+
+    if (*colorType == PNG_COLOR_TYPE_PALETTE) {
+        // Create separate RGB and Alpha palettes and set the number of colors
+        *paletteEntries = num_colors;
+
+        // Create the RGB and alpha palettes
+        for (int idx = 0; idx < num_colors; idx++) {
+            col = colors[idx];
+            rgbPalette[idx].red   = (png_byte) ((col >> 24) & 0xff);
+            rgbPalette[idx].green = (png_byte) ((col >> 16) & 0xff);
+            rgbPalette[idx].blue  = (png_byte) ((col >>  8) & 0xff);
+            alphaPalette[idx]     = (png_byte)  (col        & 0xff);
+        }
+    } else if (*colorType == PNG_COLOR_TYPE_GRAY || *colorType == PNG_COLOR_TYPE_GRAY_ALPHA) {
+        // If the image is gray or gray + alpha, compact the pixels into outRows
+        for (j = 0; j < h; j++) {
+            const png_byte* row = imageInfo.rows[j];
+            png_bytep out = outRows[j];
+            for (i = 0; i < w; i++) {
+                rr = *row++;
+                gg = *row++;
+                bb = *row++;
+                aa = *row++;
+
+                if (isGrayscale) {
+                    *out++ = rr;
+                } else {
+                    *out++ = (png_byte) (rr * 0.2126f + gg * 0.7152f + bb * 0.0722f);
+                }
+                if (!isOpaque) {
+                    *out++ = aa;
+                }
+           }
+        }
+    }
+}
+
+static bool writePng(IDiagnostics* diag, png_structp writePtr, png_infop infoPtr, PngInfo* info,
+                     int grayScaleTolerance) {
+    if (setjmp(png_jmpbuf(writePtr))) {
+        diag->error(DiagMessage() << "failed to write png");
+        return false;
+    }
+
+    uint32_t width, height;
+    int colorType, bitDepth, interlaceType, compressionType;
+
+    png_unknown_chunk unknowns[3];
+    unknowns[0].data = nullptr;
+    unknowns[1].data = nullptr;
+    unknowns[2].data = nullptr;
+
+    png_bytepp outRows = (png_bytepp) malloc((int) info->height * sizeof(png_bytep));
+    if (outRows == (png_bytepp) 0) {
+        printf("Can't allocate output buffer!\n");
+        exit(1);
+    }
+    for (uint32_t i = 0; i < info->height; i++) {
+        outRows[i] = (png_bytep) malloc(2 * (int) info->width);
+        if (outRows[i] == (png_bytep) 0) {
+            printf("Can't allocate output buffer!\n");
+            exit(1);
+        }
+    }
+
+    png_set_compression_level(writePtr, Z_BEST_COMPRESSION);
+
+    if (kDebug) {
+        diag->note(DiagMessage()
+                   << "writing image: w = " << info->width
+                   << ", h = " << info->height);
+    }
+
+    png_color rgbPalette[256];
+    png_byte alphaPalette[256];
+    bool hasTransparency;
+    int paletteEntries;
+
+    analyze_image(diag, *info, grayScaleTolerance, rgbPalette, alphaPalette,
+                  &paletteEntries, &hasTransparency, &colorType, outRows);
+
+    // If the image is a 9-patch, we need to preserve it as a ARGB file to make
+    // sure the pixels will not be pre-dithered/clamped until we decide they are
+    if (info->is9Patch && (colorType == PNG_COLOR_TYPE_RGB ||
+            colorType == PNG_COLOR_TYPE_GRAY || colorType == PNG_COLOR_TYPE_PALETTE)) {
+        colorType = PNG_COLOR_TYPE_RGB_ALPHA;
+    }
+
+    if (kDebug) {
+        switch (colorType) {
+        case PNG_COLOR_TYPE_PALETTE:
+            diag->note(DiagMessage()
+                       << "has " << paletteEntries
+                       << " colors" << (hasTransparency ? " (with alpha)" : "")
+                       << ", using PNG_COLOR_TYPE_PALLETTE");
+            break;
+        case PNG_COLOR_TYPE_GRAY:
+            diag->note(DiagMessage() << "is opaque gray, using PNG_COLOR_TYPE_GRAY");
+            break;
+        case PNG_COLOR_TYPE_GRAY_ALPHA:
+            diag->note(DiagMessage() << "is gray + alpha, using PNG_COLOR_TYPE_GRAY_ALPHA");
+            break;
+        case PNG_COLOR_TYPE_RGB:
+            diag->note(DiagMessage() << "is opaque RGB, using PNG_COLOR_TYPE_RGB");
+            break;
+        case PNG_COLOR_TYPE_RGB_ALPHA:
+            diag->note(DiagMessage() << "is RGB + alpha, using PNG_COLOR_TYPE_RGB_ALPHA");
+            break;
+        }
+    }
+
+    png_set_IHDR(writePtr, infoPtr, info->width, info->height, 8, colorType,
+                 PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
+
+    if (colorType == PNG_COLOR_TYPE_PALETTE) {
+        png_set_PLTE(writePtr, infoPtr, rgbPalette, paletteEntries);
+        if (hasTransparency) {
+            png_set_tRNS(writePtr, infoPtr, alphaPalette, paletteEntries, (png_color_16p) 0);
+        }
+        png_set_filter(writePtr, 0, PNG_NO_FILTERS);
+    } else {
+        png_set_filter(writePtr, 0, PNG_ALL_FILTERS);
+    }
+
+    if (info->is9Patch) {
+        int chunkCount = 2 + (info->haveLayoutBounds ? 1 : 0);
+        int pIndex = info->haveLayoutBounds ? 2 : 1;
+        int bIndex = 1;
+        int oIndex = 0;
+
+        // Chunks ordered thusly because older platforms depend on the base 9 patch data being last
+        png_bytep chunkNames = info->haveLayoutBounds
+                ? (png_bytep)"npOl\0npLb\0npTc\0"
+                : (png_bytep)"npOl\0npTc";
+
+        // base 9 patch data
+        if (kDebug) {
+            diag->note(DiagMessage() << "adding 9-patch info..");
+        }
+        strcpy((char*)unknowns[pIndex].name, "npTc");
+        unknowns[pIndex].data = (png_byte*) info->serialize9Patch();
+        unknowns[pIndex].size = info->info9Patch.serializedSize();
+        // TODO: remove the check below when everything works
+        checkNinePatchSerialization(&info->info9Patch, unknowns[pIndex].data);
+
+        // automatically generated 9 patch outline data
+        int chunkSize = sizeof(png_uint_32) * 6;
+        strcpy((char*)unknowns[oIndex].name, "npOl");
+        unknowns[oIndex].data = (png_byte*) calloc(chunkSize, 1);
+        png_byte outputData[chunkSize];
+        memcpy(&outputData, &info->outlineInsetsLeft, 4 * sizeof(png_uint_32));
+        ((float*) outputData)[4] = info->outlineRadius;
+        ((png_uint_32*) outputData)[5] = info->outlineAlpha;
+        memcpy(unknowns[oIndex].data, &outputData, chunkSize);
+        unknowns[oIndex].size = chunkSize;
+
+        // optional optical inset / layout bounds data
+        if (info->haveLayoutBounds) {
+            int chunkSize = sizeof(png_uint_32) * 4;
+            strcpy((char*)unknowns[bIndex].name, "npLb");
+            unknowns[bIndex].data = (png_byte*) calloc(chunkSize, 1);
+            memcpy(unknowns[bIndex].data, &info->layoutBoundsLeft, chunkSize);
+            unknowns[bIndex].size = chunkSize;
+        }
+
+        for (int i = 0; i < chunkCount; i++) {
+            unknowns[i].location = PNG_HAVE_PLTE;
+        }
+        png_set_keep_unknown_chunks(writePtr, PNG_HANDLE_CHUNK_ALWAYS,
+                                    chunkNames, chunkCount);
+        png_set_unknown_chunks(writePtr, infoPtr, unknowns, chunkCount);
+
+#if PNG_LIBPNG_VER < 10600
+        // Deal with unknown chunk location bug in 1.5.x and earlier.
+        png_set_unknown_chunk_location(writePtr, infoPtr, 0, PNG_HAVE_PLTE);
+        if (info->haveLayoutBounds) {
+            png_set_unknown_chunk_location(writePtr, infoPtr, 1, PNG_HAVE_PLTE);
+        }
+#endif
+    }
+
+    png_write_info(writePtr, infoPtr);
+
+    png_bytepp rows;
+    if (colorType == PNG_COLOR_TYPE_RGB || colorType == PNG_COLOR_TYPE_RGB_ALPHA) {
+        if (colorType == PNG_COLOR_TYPE_RGB) {
+            png_set_filler(writePtr, 0, PNG_FILLER_AFTER);
+        }
+        rows = info->rows.data();
+    } else {
+        rows = outRows;
+    }
+    png_write_image(writePtr, rows);
+
+    if (kDebug) {
+        printf("Final image data:\n");
+        //dump_image(info->width, info->height, rows, colorType);
+    }
+
+    png_write_end(writePtr, infoPtr);
+
+    for (uint32_t i = 0; i < info->height; i++) {
+        free(outRows[i]);
+    }
+    free(outRows);
+    free(unknowns[0].data);
+    free(unknowns[1].data);
+    free(unknowns[2].data);
+
+    png_get_IHDR(writePtr, infoPtr, &width, &height, &bitDepth, &colorType, &interlaceType,
+                 &compressionType, nullptr);
+
+    if (kDebug) {
+        diag->note(DiagMessage()
+                   << "image written: w = " << width << ", h = " << height
+                   << ", d = " << bitDepth << ", colors = " << colorType
+                   << ", inter = " << interlaceType << ", comp = " << compressionType);
+    }
+    return true;
+}
+
+constexpr uint32_t kColorWhite = 0xffffffffu;
+constexpr uint32_t kColorTick = 0xff000000u;
+constexpr uint32_t kColorLayoutBoundsTick = 0xff0000ffu;
+
+enum class TickType {
+    kNone,
+    kTick,
+    kLayoutBounds,
+    kBoth
+};
+
+static TickType tickType(png_bytep p, bool transparent, const char** outError) {
+    png_uint_32 color = p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
+
+    if (transparent) {
+        if (p[3] == 0) {
+            return TickType::kNone;
+        }
+        if (color == kColorLayoutBoundsTick) {
+            return TickType::kLayoutBounds;
+        }
+        if (color == kColorTick) {
+            return TickType::kTick;
+        }
+
+        // Error cases
+        if (p[3] != 0xff) {
+            *outError = "Frame pixels must be either solid or transparent "
+                        "(not intermediate alphas)";
+            return TickType::kNone;
+        }
+
+        if (p[0] != 0 || p[1] != 0 || p[2] != 0) {
+            *outError = "Ticks in transparent frame must be black or red";
+        }
+        return TickType::kTick;
+    }
+
+    if (p[3] != 0xFF) {
+        *outError = "White frame must be a solid color (no alpha)";
+    }
+    if (color == kColorWhite) {
+        return TickType::kNone;
+    }
+    if (color == kColorTick) {
+        return TickType::kTick;
+    }
+    if (color == kColorLayoutBoundsTick) {
+        return TickType::kLayoutBounds;
+    }
+
+    if (p[0] != 0 || p[1] != 0 || p[2] != 0) {
+        *outError = "Ticks in white frame must be black or red";
+        return TickType::kNone;
+    }
+    return TickType::kTick;
+}
+
+enum class TickState {
+    kStart,
+    kInside1,
+    kOutside1
+};
+
+static bool getHorizontalTicks(png_bytep row, int width, bool transparent, bool required,
+                               int32_t* outLeft, int32_t* outRight, const char** outError,
+                               uint8_t* outDivs, bool multipleAllowed) {
+    *outLeft = *outRight = -1;
+    TickState state = TickState::kStart;
+    bool found = false;
+
+    for (int i = 1; i < width - 1; i++) {
+        if (tickType(row+i*4, transparent, outError) == TickType::kTick) {
+            if (state == TickState::kStart ||
+                (state == TickState::kOutside1 && multipleAllowed)) {
+                *outLeft = i-1;
+                *outRight = width-2;
+                found = true;
+                if (outDivs != NULL) {
+                    *outDivs += 2;
+                }
+                state = TickState::kInside1;
+            } else if (state == TickState::kOutside1) {
+                *outError = "Can't have more than one marked region along edge";
+                *outLeft = i;
+                return false;
+            }
+        } else if (!*outError) {
+            if (state == TickState::kInside1) {
+                // We're done with this div.  Move on to the next.
+                *outRight = i-1;
+                outRight += 2;
+                outLeft += 2;
+                state = TickState::kOutside1;
+            }
+        } else {
+            *outLeft = i;
+            return false;
+        }
+    }
+
+    if (required && !found) {
+        *outError = "No marked region found along edge";
+        *outLeft = -1;
+        return false;
+    }
+    return true;
+}
+
+static bool getVerticalTicks(png_bytepp rows, int offset, int height, bool transparent,
+                             bool required, int32_t* outTop, int32_t* outBottom,
+                             const char** outError, uint8_t* outDivs, bool multipleAllowed) {
+    *outTop = *outBottom = -1;
+    TickState state = TickState::kStart;
+    bool found = false;
+
+    for (int i = 1; i < height - 1; i++) {
+        if (tickType(rows[i]+offset, transparent, outError) == TickType::kTick) {
+            if (state == TickState::kStart ||
+                (state == TickState::kOutside1 && multipleAllowed)) {
+                *outTop = i-1;
+                *outBottom = height-2;
+                found = true;
+                if (outDivs != NULL) {
+                    *outDivs += 2;
+                }
+                state = TickState::kInside1;
+            } else if (state == TickState::kOutside1) {
+                *outError = "Can't have more than one marked region along edge";
+                *outTop = i;
+                return false;
+            }
+        } else if (!*outError) {
+            if (state == TickState::kInside1) {
+                // We're done with this div.  Move on to the next.
+                *outBottom = i-1;
+                outTop += 2;
+                outBottom += 2;
+                state = TickState::kOutside1;
+            }
+        } else {
+            *outTop = i;
+            return false;
+        }
+    }
+
+    if (required && !found) {
+        *outError = "No marked region found along edge";
+        *outTop = -1;
+        return false;
+    }
+    return true;
+}
+
+static bool getHorizontalLayoutBoundsTicks(png_bytep row, int width, bool transparent,
+                                           bool /* required */, int32_t* outLeft,
+                                           int32_t* outRight, const char** outError) {
+    *outLeft = *outRight = 0;
+
+    // Look for left tick
+    if (tickType(row + 4, transparent, outError) == TickType::kLayoutBounds) {
+        // Starting with a layout padding tick
+        int i = 1;
+        while (i < width - 1) {
+            (*outLeft)++;
+            i++;
+            if (tickType(row + i * 4, transparent, outError) != TickType::kLayoutBounds) {
+                break;
+            }
+        }
+    }
+
+    // Look for right tick
+    if (tickType(row + (width - 2) * 4, transparent, outError) == TickType::kLayoutBounds) {
+        // Ending with a layout padding tick
+        int i = width - 2;
+        while (i > 1) {
+            (*outRight)++;
+            i--;
+            if (tickType(row+i*4, transparent, outError) != TickType::kLayoutBounds) {
+                break;
+            }
+        }
+    }
+    return true;
+}
+
+static bool getVerticalLayoutBoundsTicks(png_bytepp rows, int offset, int height, bool transparent,
+                                         bool /* required */, int32_t* outTop, int32_t* outBottom,
+                                         const char** outError) {
+    *outTop = *outBottom = 0;
+
+    // Look for top tick
+    if (tickType(rows[1] + offset, transparent, outError) == TickType::kLayoutBounds) {
+        // Starting with a layout padding tick
+        int i = 1;
+        while (i < height - 1) {
+            (*outTop)++;
+            i++;
+            if (tickType(rows[i] + offset, transparent, outError) != TickType::kLayoutBounds) {
+                break;
+            }
+        }
+    }
+
+    // Look for bottom tick
+    if (tickType(rows[height - 2] + offset, transparent, outError) == TickType::kLayoutBounds) {
+        // Ending with a layout padding tick
+        int i = height - 2;
+        while (i > 1) {
+            (*outBottom)++;
+            i--;
+            if (tickType(rows[i] + offset, transparent, outError) != TickType::kLayoutBounds) {
+                break;
+            }
+        }
+    }
+    return true;
+}
+
+static void findMaxOpacity(png_bytepp rows, int startX, int startY, int endX, int endY,
+                           int dX, int dY, int* outInset) {
+    uint8_t maxOpacity = 0;
+    int inset = 0;
+    *outInset = 0;
+    for (int x = startX, y = startY; x != endX && y != endY; x += dX, y += dY, inset++) {
+        png_byte* color = rows[y] + x * 4;
+        uint8_t opacity = color[3];
+        if (opacity > maxOpacity) {
+            maxOpacity = opacity;
+            *outInset = inset;
+        }
+        if (opacity == 0xff) return;
+    }
+}
+
+static uint8_t maxAlphaOverRow(png_bytep row, int startX, int endX) {
+    uint8_t maxAlpha = 0;
+    for (int x = startX; x < endX; x++) {
+        uint8_t alpha = (row + x * 4)[3];
+        if (alpha > maxAlpha) maxAlpha = alpha;
+    }
+    return maxAlpha;
+}
+
+static uint8_t maxAlphaOverCol(png_bytepp rows, int offsetX, int startY, int endY) {
+    uint8_t maxAlpha = 0;
+    for (int y = startY; y < endY; y++) {
+        uint8_t alpha = (rows[y] + offsetX * 4)[3];
+        if (alpha > maxAlpha) maxAlpha = alpha;
+    }
+    return maxAlpha;
+}
+
+static void getOutline(PngInfo* image) {
+    int midX = image->width / 2;
+    int midY = image->height / 2;
+    int endX = image->width - 2;
+    int endY = image->height - 2;
+
+    // find left and right extent of nine patch content on center row
+    if (image->width > 4) {
+        findMaxOpacity(image->rows.data(), 1, midY, midX, -1, 1, 0, &image->outlineInsetsLeft);
+        findMaxOpacity(image->rows.data(), endX, midY, midX, -1, -1, 0,
+                       &image->outlineInsetsRight);
+    } else {
+        image->outlineInsetsLeft = 0;
+        image->outlineInsetsRight = 0;
+    }
+
+    // find top and bottom extent of nine patch content on center column
+    if (image->height > 4) {
+        findMaxOpacity(image->rows.data(), midX, 1, -1, midY, 0, 1, &image->outlineInsetsTop);
+        findMaxOpacity(image->rows.data(), midX, endY, -1, midY, 0, -1,
+                       &image->outlineInsetsBottom);
+    } else {
+        image->outlineInsetsTop = 0;
+        image->outlineInsetsBottom = 0;
+    }
+
+    int innerStartX = 1 + image->outlineInsetsLeft;
+    int innerStartY = 1 + image->outlineInsetsTop;
+    int innerEndX = endX - image->outlineInsetsRight;
+    int innerEndY = endY - image->outlineInsetsBottom;
+    int innerMidX = (innerEndX + innerStartX) / 2;
+    int innerMidY = (innerEndY + innerStartY) / 2;
+
+    // assuming the image is a round rect, compute the radius by marching
+    // diagonally from the top left corner towards the center
+    image->outlineAlpha = std::max(
+            maxAlphaOverRow(image->rows[innerMidY], innerStartX, innerEndX),
+            maxAlphaOverCol(image->rows.data(), innerMidX, innerStartY, innerStartY));
+
+    int diagonalInset = 0;
+    findMaxOpacity(image->rows.data(), innerStartX, innerStartY, innerMidX, innerMidY, 1, 1,
+                   &diagonalInset);
+
+    /* Determine source radius based upon inset:
+     *     sqrt(r^2 + r^2) = sqrt(i^2 + i^2) + r
+     *     sqrt(2) * r = sqrt(2) * i + r
+     *     (sqrt(2) - 1) * r = sqrt(2) * i
+     *     r = sqrt(2) / (sqrt(2) - 1) * i
+     */
+    image->outlineRadius = 3.4142f * diagonalInset;
+
+    if (kDebug) {
+        printf("outline insets %d %d %d %d, rad %f, alpha %x\n",
+                image->outlineInsetsLeft,
+                image->outlineInsetsTop,
+                image->outlineInsetsRight,
+                image->outlineInsetsBottom,
+                image->outlineRadius,
+                image->outlineAlpha);
+    }
+}
+
+static uint32_t getColor(png_bytepp rows, int left, int top, int right, int bottom) {
+    png_bytep color = rows[top] + left*4;
+
+    if (left > right || top > bottom) {
+        return android::Res_png_9patch::TRANSPARENT_COLOR;
+    }
+
+    while (top <= bottom) {
+        for (int i = left; i <= right; i++) {
+            png_bytep p = rows[top]+i*4;
+            if (color[3] == 0) {
+                if (p[3] != 0) {
+                    return android::Res_png_9patch::NO_COLOR;
+                }
+            } else if (p[0] != color[0] || p[1] != color[1] ||
+                    p[2] != color[2] || p[3] != color[3]) {
+                return android::Res_png_9patch::NO_COLOR;
+            }
+        }
+        top++;
+    }
+
+    if (color[3] == 0) {
+        return android::Res_png_9patch::TRANSPARENT_COLOR;
+    }
+    return (color[3]<<24) | (color[0]<<16) | (color[1]<<8) | color[2];
+}
+
+static bool do9Patch(PngInfo* image, std::string* outError) {
+    image->is9Patch = true;
+
+    int W = image->width;
+    int H = image->height;
+    int i, j;
+
+    const int maxSizeXDivs = W * sizeof(int32_t);
+    const int maxSizeYDivs = H * sizeof(int32_t);
+    int32_t* xDivs = image->xDivs = new int32_t[W];
+    int32_t* yDivs = image->yDivs = new int32_t[H];
+    uint8_t numXDivs = 0;
+    uint8_t numYDivs = 0;
+
+    int8_t numColors;
+    int numRows;
+    int numCols;
+    int top;
+    int left;
+    int right;
+    int bottom;
+    memset(xDivs, -1, maxSizeXDivs);
+    memset(yDivs, -1, maxSizeYDivs);
+    image->info9Patch.paddingLeft = image->info9Patch.paddingRight = -1;
+    image->info9Patch.paddingTop = image->info9Patch.paddingBottom = -1;
+    image->layoutBoundsLeft = image->layoutBoundsRight = 0;
+    image->layoutBoundsTop = image->layoutBoundsBottom = 0;
+
+    png_bytep p = image->rows[0];
+    bool transparent = p[3] == 0;
+    bool hasColor = false;
+
+    const char* errorMsg = nullptr;
+    int errorPixel = -1;
+    const char* errorEdge = nullptr;
+
+    int colorIndex = 0;
+    std::vector<png_bytep> newRows;
+
+    // Validate size...
+    if (W < 3 || H < 3) {
+        errorMsg = "Image must be at least 3x3 (1x1 without frame) pixels";
+        goto getout;
+    }
+
+    // Validate frame...
+    if (!transparent &&
+            (p[0] != 0xFF || p[1] != 0xFF || p[2] != 0xFF || p[3] != 0xFF)) {
+        errorMsg = "Must have one-pixel frame that is either transparent or white";
+        goto getout;
+    }
+
+    // Find left and right of sizing areas...
+    if (!getHorizontalTicks(p, W, transparent, true, &xDivs[0], &xDivs[1], &errorMsg, &numXDivs,
+                            true)) {
+        errorPixel = xDivs[0];
+        errorEdge = "top";
+        goto getout;
+    }
+
+    // Find top and bottom of sizing areas...
+    if (!getVerticalTicks(image->rows.data(), 0, H, transparent, true, &yDivs[0], &yDivs[1],
+                          &errorMsg, &numYDivs, true)) {
+        errorPixel = yDivs[0];
+        errorEdge = "left";
+        goto getout;
+    }
+
+    // Copy patch size data into image...
+    image->info9Patch.numXDivs = numXDivs;
+    image->info9Patch.numYDivs = numYDivs;
+
+    // Find left and right of padding area...
+    if (!getHorizontalTicks(image->rows[H-1], W, transparent, false,
+                            &image->info9Patch.paddingLeft, &image->info9Patch.paddingRight,
+                            &errorMsg, nullptr, false)) {
+        errorPixel = image->info9Patch.paddingLeft;
+        errorEdge = "bottom";
+        goto getout;
+    }
+
+    // Find top and bottom of padding area...
+    if (!getVerticalTicks(image->rows.data(), (W-1)*4, H, transparent, false,
+                          &image->info9Patch.paddingTop, &image->info9Patch.paddingBottom,
+                          &errorMsg, nullptr, false)) {
+        errorPixel = image->info9Patch.paddingTop;
+        errorEdge = "right";
+        goto getout;
+    }
+
+    // Find left and right of layout padding...
+    getHorizontalLayoutBoundsTicks(image->rows[H-1], W, transparent, false,
+                                   &image->layoutBoundsLeft, &image->layoutBoundsRight, &errorMsg);
+
+    getVerticalLayoutBoundsTicks(image->rows.data(), (W-1)*4, H, transparent, false,
+                                 &image->layoutBoundsTop, &image->layoutBoundsBottom, &errorMsg);
+
+    image->haveLayoutBounds = image->layoutBoundsLeft != 0
+                               || image->layoutBoundsRight != 0
+                               || image->layoutBoundsTop != 0
+                               || image->layoutBoundsBottom != 0;
+
+    if (image->haveLayoutBounds) {
+        if (kDebug) {
+            printf("layoutBounds=%d %d %d %d\n", image->layoutBoundsLeft, image->layoutBoundsTop,
+                    image->layoutBoundsRight, image->layoutBoundsBottom);
+        }
+    }
+
+    // use opacity of pixels to estimate the round rect outline
+    getOutline(image);
+
+    // If padding is not yet specified, take values from size.
+    if (image->info9Patch.paddingLeft < 0) {
+        image->info9Patch.paddingLeft = xDivs[0];
+        image->info9Patch.paddingRight = W - 2 - xDivs[1];
+    } else {
+        // Adjust value to be correct!
+        image->info9Patch.paddingRight = W - 2 - image->info9Patch.paddingRight;
+    }
+    if (image->info9Patch.paddingTop < 0) {
+        image->info9Patch.paddingTop = yDivs[0];
+        image->info9Patch.paddingBottom = H - 2 - yDivs[1];
+    } else {
+        // Adjust value to be correct!
+        image->info9Patch.paddingBottom = H - 2 - image->info9Patch.paddingBottom;
+    }
+
+/*    if (kDebug) {
+        printf("Size ticks for %s: x0=%d, x1=%d, y0=%d, y1=%d\n", imageName,
+                xDivs[0], xDivs[1],
+                yDivs[0], yDivs[1]);
+        printf("padding ticks for %s: l=%d, r=%d, t=%d, b=%d\n", imageName,
+                image->info9Patch.paddingLeft, image->info9Patch.paddingRight,
+                image->info9Patch.paddingTop, image->info9Patch.paddingBottom);
+    }*/
+
+    // Remove frame from image.
+    newRows.resize(H - 2);
+    for (i = 0; i < H - 2; i++) {
+        newRows[i] = image->rows[i + 1];
+        memmove(newRows[i], newRows[i] + 4, (W - 2) * 4);
+    }
+    image->rows.swap(newRows);
+
+    image->width -= 2;
+    W = image->width;
+    image->height -= 2;
+    H = image->height;
+
+    // Figure out the number of rows and columns in the N-patch
+    numCols = numXDivs + 1;
+    if (xDivs[0] == 0) {  // Column 1 is strechable
+        numCols--;
+    }
+    if (xDivs[numXDivs - 1] == W) {
+        numCols--;
+    }
+    numRows = numYDivs + 1;
+    if (yDivs[0] == 0) {  // Row 1 is strechable
+        numRows--;
+    }
+    if (yDivs[numYDivs - 1] == H) {
+        numRows--;
+    }
+
+    // Make sure the amount of rows and columns will fit in the number of
+    // colors we can use in the 9-patch format.
+    if (numRows * numCols > 0x7F) {
+        errorMsg = "Too many rows and columns in 9-patch perimeter";
+        goto getout;
+    }
+
+    numColors = numRows * numCols;
+    image->info9Patch.numColors = numColors;
+    image->colors.resize(numColors);
+
+    // Fill in color information for each patch.
+
+    uint32_t c;
+    top = 0;
+
+    // The first row always starts with the top being at y=0 and the bottom
+    // being either yDivs[1] (if yDivs[0]=0) of yDivs[0].  In the former case
+    // the first row is stretchable along the Y axis, otherwise it is fixed.
+    // The last row always ends with the bottom being bitmap.height and the top
+    // being either yDivs[numYDivs-2] (if yDivs[numYDivs-1]=bitmap.height) or
+    // yDivs[numYDivs-1]. In the former case the last row is stretchable along
+    // the Y axis, otherwise it is fixed.
+    //
+    // The first and last columns are similarly treated with respect to the X
+    // axis.
+    //
+    // The above is to help explain some of the special casing that goes on the
+    // code below.
+
+    // The initial yDiv and whether the first row is considered stretchable or
+    // not depends on whether yDiv[0] was zero or not.
+    for (j = (yDivs[0] == 0 ? 1 : 0); j <= numYDivs && top < H; j++) {
+        if (j == numYDivs) {
+            bottom = H;
+        } else {
+            bottom = yDivs[j];
+        }
+        left = 0;
+        // The initial xDiv and whether the first column is considered
+        // stretchable or not depends on whether xDiv[0] was zero or not.
+        for (i = xDivs[0] == 0 ? 1 : 0; i <= numXDivs && left < W; i++) {
+            if (i == numXDivs) {
+                right = W;
+            } else {
+                right = xDivs[i];
+            }
+            c = getColor(image->rows.data(), left, top, right - 1, bottom - 1);
+            image->colors[colorIndex++] = c;
+            if (kDebug) {
+                if (c != android::Res_png_9patch::NO_COLOR) {
+                    hasColor = true;
+                }
+            }
+            left = right;
+        }
+        top = bottom;
+    }
+
+    assert(colorIndex == numColors);
+
+    if (kDebug && hasColor) {
+        for (i = 0; i < numColors; i++) {
+            if (i == 0) printf("Colors:\n");
+            printf(" #%08x", image->colors[i]);
+            if (i == numColors - 1) printf("\n");
+        }
+    }
+getout:
+    if (errorMsg) {
+        std::stringstream err;
+        err << "9-patch malformed: " << errorMsg;
+        if (!errorEdge) {
+            err << "." << std::endl;
+            if (errorPixel >= 0) {
+                err << "Found at pixel #" << errorPixel << " along " << errorEdge << " edge";
+            } else {
+                err << "Found along " << errorEdge << " edge";
+            }
+        }
+        *outError = err.str();
+        return false;
+    }
+    return true;
+}
+
+
+bool Png::process(const Source& source, std::istream* input, BigBuffer* outBuffer,
+                  const PngOptions& options) {
+    png_byte signature[kPngSignatureSize];
+
+    // Read the PNG signature first.
+    if (!input->read(reinterpret_cast<char*>(signature), kPngSignatureSize)) {
+        mDiag->error(DiagMessage() << strerror(errno));
+        return false;
+    }
+
+    // If the PNG signature doesn't match, bail early.
+    if (png_sig_cmp(signature, 0, kPngSignatureSize) != 0) {
+        mDiag->error(DiagMessage() << "not a valid png file");
+        return false;
+    }
+
+    bool result = false;
+    png_structp readPtr = nullptr;
+    png_infop infoPtr = nullptr;
+    png_structp writePtr = nullptr;
+    png_infop writeInfoPtr = nullptr;
+    PngInfo pngInfo = {};
+
+    readPtr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, nullptr, nullptr);
+    if (!readPtr) {
+        mDiag->error(DiagMessage() << "failed to allocate read ptr");
+        goto bail;
+    }
+
+    infoPtr = png_create_info_struct(readPtr);
+    if (!infoPtr) {
+        mDiag->error(DiagMessage() << "failed to allocate info ptr");
+        goto bail;
+    }
+
+    png_set_error_fn(readPtr, reinterpret_cast<png_voidp>(mDiag), nullptr, logWarning);
+
+    // Set the read function to read from std::istream.
+    png_set_read_fn(readPtr, (png_voidp) input, readDataFromStream);
+
+    if (!readPng(mDiag, readPtr, infoPtr, &pngInfo)) {
+        goto bail;
+    }
+
+    if (util::stringEndsWith<char>(source.path, ".9.png")) {
+        std::string errorMsg;
+        if (!do9Patch(&pngInfo, &errorMsg)) {
+            mDiag->error(DiagMessage() << errorMsg);
+            goto bail;
+        }
+    }
+
+    writePtr = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, nullptr, nullptr);
+    if (!writePtr) {
+        mDiag->error(DiagMessage() << "failed to allocate write ptr");
+        goto bail;
+    }
+
+    writeInfoPtr = png_create_info_struct(writePtr);
+    if (!writeInfoPtr) {
+        mDiag->error(DiagMessage() << "failed to allocate write info ptr");
+        goto bail;
+    }
+
+    png_set_error_fn(writePtr, nullptr, nullptr, logWarning);
+
+    // Set the write function to write to std::ostream.
+    png_set_write_fn(writePtr, (png_voidp)outBuffer, writeDataToStream, flushDataToStream);
+
+    if (!writePng(mDiag, writePtr, writeInfoPtr, &pngInfo, options.grayScaleTolerance)) {
+        goto bail;
+    }
+
+    result = true;
+bail:
+    if (readPtr) {
+        png_destroy_read_struct(&readPtr, &infoPtr, nullptr);
+    }
+
+    if (writePtr) {
+        png_destroy_write_struct(&writePtr, &writeInfoPtr);
+    }
+    return result;
+}
+
+} // namespace aapt
diff --git a/tools/aapt2/compile/Png.h b/tools/aapt2/compile/Png.h
new file mode 100644
index 0000000..345ff6c
--- /dev/null
+++ b/tools/aapt2/compile/Png.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef AAPT_PNG_H
+#define AAPT_PNG_H
+
+#include "util/BigBuffer.h"
+#include "Diagnostics.h"
+#include "Source.h"
+
+#include <iostream>
+#include <string>
+
+namespace aapt {
+
+struct PngOptions {
+    int grayScaleTolerance = 0;
+};
+
+class Png {
+public:
+    Png(IDiagnostics* diag) : mDiag(diag) {
+    }
+
+    bool process(const Source& source, std::istream* input, BigBuffer* outBuffer,
+                 const PngOptions& options);
+
+private:
+    IDiagnostics* mDiag;
+};
+
+} // namespace aapt
+
+#endif // AAPT_PNG_H
diff --git a/tools/aapt2/compile/XmlIdCollector.cpp b/tools/aapt2/compile/XmlIdCollector.cpp
new file mode 100644
index 0000000..dfdf710
--- /dev/null
+++ b/tools/aapt2/compile/XmlIdCollector.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ResourceUtils.h"
+#include "ResourceValues.h"
+#include "XmlDom.h"
+
+#include "compile/XmlIdCollector.h"
+
+#include <algorithm>
+#include <vector>
+
+namespace aapt {
+
+namespace {
+
+static bool cmpName(const SourcedResourceName& a, const ResourceNameRef& b) {
+    return a.name < b;
+}
+
+struct IdCollector : public xml::Visitor {
+    using xml::Visitor::visit;
+
+    std::vector<SourcedResourceName>* mOutSymbols;
+
+    IdCollector(std::vector<SourcedResourceName>* outSymbols) : mOutSymbols(outSymbols) {
+    }
+
+    void visit(xml::Element* element) override {
+        for (xml::Attribute& attr : element->attributes) {
+            ResourceNameRef name;
+            bool create = false;
+            if (ResourceUtils::tryParseReference(attr.value, &name, &create, nullptr)) {
+                if (create && name.type == ResourceType::kId) {
+                    auto iter = std::lower_bound(mOutSymbols->begin(), mOutSymbols->end(),
+                                                 name, cmpName);
+                    if (iter == mOutSymbols->end() || iter->name != name) {
+                        mOutSymbols->insert(iter, SourcedResourceName{ name.toResourceName(),
+                                                                       element->lineNumber });
+                    }
+                }
+            }
+        }
+
+        xml::Visitor::visit(element);
+    }
+};
+
+} // namespace
+
+bool XmlIdCollector::consume(IAaptContext* context, XmlResource* xmlRes) {
+    xmlRes->file.exportedSymbols.clear();
+    IdCollector collector(&xmlRes->file.exportedSymbols);
+    xmlRes->root->accept(&collector);
+    return true;
+}
+
+} // namespace aapt
diff --git a/tools/aapt2/compile/XmlIdCollector.h b/tools/aapt2/compile/XmlIdCollector.h
new file mode 100644
index 0000000..96a58f2
--- /dev/null
+++ b/tools/aapt2/compile/XmlIdCollector.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef AAPT_XMLIDCOLLECTOR_H
+#define AAPT_XMLIDCOLLECTOR_H
+
+#include "process/IResourceTableConsumer.h"
+
+namespace aapt {
+
+struct XmlIdCollector : public IXmlResourceConsumer {
+    bool consume(IAaptContext* context, XmlResource* xmlRes) override;
+};
+
+} // namespace aapt
+
+#endif /* AAPT_XMLIDCOLLECTOR_H */
diff --git a/tools/aapt2/compile/XmlIdCollector_test.cpp b/tools/aapt2/compile/XmlIdCollector_test.cpp
new file mode 100644
index 0000000..c703f451
--- /dev/null
+++ b/tools/aapt2/compile/XmlIdCollector_test.cpp
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "compile/XmlIdCollector.h"
+#include "test/Builders.h"
+#include "test/Context.h"
+
+#include <algorithm>
+#include <gtest/gtest.h>
+
+namespace aapt {
+
+TEST(XmlIdCollectorTest, CollectsIds) {
+    std::unique_ptr<IAaptContext> context = test::ContextBuilder().build();
+
+    std::unique_ptr<XmlResource> doc = test::buildXmlDom(R"EOF(
+            <View xmlns:android="http://schemas.android.com/apk/res/android"
+                  android:id="@+id/foo"
+                  text="@+id/bar">
+              <SubView android:id="@+id/car"
+                       class="@+id/bar"/>
+            </View>)EOF");
+
+    XmlIdCollector collector;
+    ASSERT_TRUE(collector.consume(context.get(), doc.get()));
+
+    EXPECT_EQ(1u, std::count(doc->file.exportedSymbols.begin(), doc->file.exportedSymbols.end(),
+                             SourcedResourceName{ test::parseNameOrDie(u"@id/foo"), 3u }));
+
+    EXPECT_EQ(1u, std::count(doc->file.exportedSymbols.begin(), doc->file.exportedSymbols.end(),
+                             SourcedResourceName{ test::parseNameOrDie(u"@id/bar"), 3u }));
+
+    EXPECT_EQ(1u, std::count(doc->file.exportedSymbols.begin(), doc->file.exportedSymbols.end(),
+                             SourcedResourceName{ test::parseNameOrDie(u"@id/car"), 6u }));
+}
+
+TEST(XmlIdCollectorTest, DontCollectNonIds) {
+    std::unique_ptr<IAaptContext> context = test::ContextBuilder().build();
+
+    std::unique_ptr<XmlResource> doc = test::buildXmlDom("<View foo=\"@+string/foo\"/>");
+
+    XmlIdCollector collector;
+    ASSERT_TRUE(collector.consume(context.get(), doc.get()));
+
+    EXPECT_TRUE(doc->file.exportedSymbols.empty());
+}
+
+} // namespace aapt