gm/imagemasksubset.cpp

/*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "gm.h"
#include "sk_tool_utils.h"
#include "SkCanvas.h"
#include "SkImage.h"
#include "SkImageGenerator.h"
#include "SkMakeUnique.h"
#include "SkSurface.h"

namespace {

const SkISize   kSize = SkISize::Make(100, 100);
const SkIRect kSubset = SkIRect::MakeLTRB(25, 25, 75, 75);
const SkRect    kDest = SkRect::MakeXYWH(10, 10, 100, 100);

sk_sp<SkImage> make_mask(const sk_sp<SkSurface>& surface) {
    sk_tool_utils::draw_checkerboard(surface->getCanvas(), 0x80808080, 0x00000000, 5);
    return surface->makeImageSnapshot();
}

class MaskGenerator final : public SkImageGenerator {
public:
    MaskGenerator(const SkImageInfo& info) : INHERITED(info) {}

    bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, SkPMColor*,
                     int*) override {
        if (info.colorType() == kIndex_8_SkColorType) {
            return false;
        }

        SkImageInfo surfaceInfo = info;
        if (kAlpha_8_SkColorType == info.colorType()) {
            surfaceInfo = surfaceInfo.makeColorSpace(nullptr);
        }

        make_mask(SkSurface::MakeRasterDirect(surfaceInfo, pixels, rowBytes));
        return true;
    }

private:
    typedef SkImageGenerator INHERITED;
};

using MakerT = sk_sp<SkImage>(*)(SkCanvas*, const SkImageInfo&);
const MakerT makers[] = {
    // SkImage_Raster
    [](SkCanvas*, const SkImageInfo& info) -> sk_sp<SkImage> {
        return make_mask(SkSurface::MakeRaster(info));
    },

    // SkImage_Gpu
    [](SkCanvas* c, const SkImageInfo& info) -> sk_sp<SkImage> {
        sk_sp<SkSurface> surface;
#if SK_SUPPORT_GPU
        surface = SkSurface::MakeRenderTarget(c->getGrContext(), SkBudgeted::kNo, info);
#endif
        return make_mask(surface ? surface : SkSurface::MakeRaster(info));
    },

    // SkImage_Generator
    [](SkCanvas*, const SkImageInfo& info) -> sk_sp<SkImage> {
        return SkImage::MakeFromGenerator(skstd::make_unique<MaskGenerator>(info));
    },
};

} // anonymous ns

// Checks whether subset SkImages preserve the original color type (A8 in this case).
DEF_SIMPLE_GM(imagemasksubset, canvas, 480, 480) {
    SkPaint paint;
    paint.setColor(0xff00ff00);

    const SkImageInfo info = SkImageInfo::MakeA8(kSize.width(), kSize.height());

    for (size_t i = 0; i < SK_ARRAY_COUNT(makers); ++i) {
        sk_sp<SkImage> image = makers[i](canvas, info);
        if (image) {
            canvas->drawImageRect(image, SkRect::Make(kSubset), kDest, &paint);
            sk_sp<SkImage> subset = image->makeSubset(kSubset);
            canvas->drawImageRect(subset, kDest.makeOffset(kSize.width() * 1.5f, 0), &paint);
        }
        canvas->translate(0, kSize.height() * 1.5f);
    }
}