gm/alphagradients.cpp

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "gm/gm.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkColor.h"
#include "include/core/SkPaint.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRect.h"
#include "include/core/SkShader.h"
#include "include/core/SkSize.h"
#include "include/core/SkString.h"
#include "include/core/SkTileMode.h"
#include "include/core/SkTypes.h"
#include "include/effects/SkGradientShader.h"

class AlphaGradientsGM : public skiagm::GM {
public:
    AlphaGradientsGM() {}

protected:
    SkString getName() const override { return SkString("alphagradients"); }

    SkISize getISize() override { return SkISize::Make(640, 480); }

    static void draw_grad(SkCanvas* canvas, const SkRect& r,
                          SkColor c0, SkColor c1, bool doPreMul) {
        SkColor colors[] = { c0, c1 };
        SkPoint pts[] = { { r.fLeft, r.fTop }, { r.fRight, r.fBottom } };
        SkPaint paint;
        uint32_t flags = doPreMul ? SkGradientShader::kInterpolateColorsInPremul_Flag : 0;
        paint.setShader(SkGradientShader::MakeLinear(pts, colors, nullptr, 2,
                                                     SkTileMode::kClamp, flags, nullptr));
        canvas->drawRect(r, paint);

        paint.setShader(nullptr);
        paint.setStyle(SkPaint::kStroke_Style);
        canvas->drawRect(r, paint);
    }

    void onDraw(SkCanvas* canvas) override {
        constexpr struct {
            SkColor fColor0;
            SkColor fColor1;
        } gRec[] = {
            { 0xFFFFFFFF, 0x00000000 },
            { 0xFFFFFFFF, 0x00FF0000 },
            { 0xFFFFFFFF, 0x00FFFF00 },
            { 0xFFFFFFFF, 0x00FFFFFF },
            { 0xFFFF0000, 0x00000000 },
            { 0xFFFF0000, 0x00FF0000 },
            { 0xFFFF0000, 0x00FFFF00 },
            { 0xFFFF0000, 0x00FFFFFF },
            { 0xFF0000FF, 0x00000000 },
            { 0xFF0000FF, 0x00FF0000 },
            { 0xFF0000FF, 0x00FFFF00 },
            { 0xFF0000FF, 0x00FFFFFF },
        };

        SkRect r = SkRect::MakeWH(300, 30);

        canvas->translate(10, 10);

        for (int doPreMul = 0; doPreMul <= 1; ++doPreMul) {
            canvas->save();
            for (size_t i = 0; i < std::size(gRec); ++i) {
                draw_grad(canvas, r, gRec[i].fColor0, gRec[i].fColor1, SkToBool(doPreMul));
                canvas->translate(0, r.height() + 8);
            }
            canvas->restore();
            canvas->translate(r.width() + 10, 0);
        }
    }

private:
    using INHERITED = skiagm::GM;
};

DEF_GM(return new AlphaGradientsGM;)