grab from latest android
git-svn-id: http://skia.googlecode.com/svn/trunk@27 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/experimental/SkSetPoly3To3_D.cpp b/experimental/SkSetPoly3To3_D.cpp
new file mode 100644
index 0000000..72ee9b1
--- /dev/null
+++ b/experimental/SkSetPoly3To3_D.cpp
@@ -0,0 +1,65 @@
+#include "SkMatrix.h"
+
+typedef int64_t SkDScalar;
+
+static SkScalar SkDScalar_toScalar(SkDScalar value) {
+ SkDScalar result = (value + (1 << 15)) >> 16;
+ int top = result >> 31;
+ SkASSERT(top == 0 || top == -1);
+ return (SkScalar)result;
+}
+
+static SkDScalar SkDScalar_setMul(SkScalar a, SkScalar b) {
+ return (SkDScalar)a * b;
+}
+
+static void computeOuterProduct(SkMatrix* matrix,
+ const SkPoint pts0[3], const SkPoint& ave0,
+ const SkPoint pts1[3], const SkPoint& ave1) {
+ SkDScalar tmp[4];
+ bzero(tmp, sizeof(tmp));
+
+ for (int i = 0; i < 3; i++) {
+ SkScalar x0 = pts0[i].fX - ave0.fX;
+ SkScalar y0 = pts0[i].fY - ave0.fY;
+ SkScalar x1 = pts1[i].fX - ave1.fX;
+ SkScalar y1 = pts1[i].fY - ave1.fY;
+ tmp[0] += SkDScalar_setMul(x0, x1);
+ tmp[1] += SkDScalar_setMul(x0, y1);
+ tmp[2] += SkDScalar_setMul(y0, x1);
+ tmp[3] += SkDScalar_setMul(y0, y1);
+ }
+ matrix->reset();
+ matrix->setScaleX(SkDScalar_toScalar(tmp[0]));
+ matrix->setSkewY( SkDScalar_toScalar(tmp[1]));
+ matrix->setSkewX( SkDScalar_toScalar(tmp[2]));
+ matrix->setScaleY(SkDScalar_toScalar(tmp[3]));
+}
+
+static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
+ return SkDScalar_toScalar(SkDScalar_setMul(ax, bx) +
+ SkDScalar_setMul(ay, by));
+}
+
+bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) {
+ const SkPoint& srcAve = src[0];
+ const SkPoint& dstAve = dst[0];
+
+ SkMatrix srcOP, dstOP;
+
+ computeOuterProduct(&srcOP, src, srcAve, src, srcAve);
+
+ if (!srcOP.invert(&srcOP)) {
+ return false;
+ }
+
+ computeOuterProduct(&dstOP, src, srcAve, dst, dstAve);
+
+ matrix->setConcat(dstOP, srcOP);
+ matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY,
+ matrix->getScaleX(), matrix->getSkewX()));
+ matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY,
+ matrix->getSkewY(), matrix->getScaleY()));
+ return true;
+}
+