SkPixelIterator.h

/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#ifndef SkPixelIterator_DEFINED
#define SkPixelIterator_DEFINED

#include "SkBitmap.h"

template <typename T>
class SkPixelIterator {
public:
    struct Pixel {
        SkIPoint pt;
        const T* addr;
    };
    struct Iter {
        Pixel operator*() const { return {{fX, fY}, fPtr}; }
        bool operator!=(const Iter& o) const { return fY != o.fY || fX != o.fX; }
        void operator++() {
            ++fX;
            ++fPtr;
            if (fX == fWidth) {
                ++fY;
                fX = 0;
                fPtr += fPad;
            }
        }
        int fX, fY, fWidth, fPad;
        const T* fPtr;
    };
    SkPixelIterator(const SkPixmap& pm)
        : fAddr((const T*)pm.addr())
        , fWidth(pm.width())
        , fHeight(pm.height())
        , fPad(pm.rowBytesAsPixels() - pm.width()) {
        SkASSERT(sizeof(T) == SkColorTypeBytesPerPixel(pm.colorType()));
    }
    SkPixelIterator(const SkBitmap& bm) : SkPixelIterator(MakePixmap(bm)) {}
    Iter begin() const { return Iter{0, 0,       fWidth, fPad, fAddr}; }
    Iter end()   const { return Iter{0, fHeight, fWidth, fPad, fAddr}; }

private:
    const T* fAddr;
    int fWidth, fHeight, fPad;
    static SkPixmap MakePixmap(const SkBitmap& bm) {
        SkPixmap pm;
        bm.peekPixels(&pm);
        return pm;
    }
};

using SkPixelIterator32 = SkPixelIterator<uint32_t>;
using SkPixelIterator16 = SkPixelIterator<uint16_t>;
using SkPixelIterator8 = SkPixelIterator<uint8_t>;

#endif  // SkPixelIterator_DEFINED

/////////////////////////////////////////////////////////////////////////////////////////////

#include "SkPixelIterator.h"
#include "Test.h"
DEF_TEST(Bitmap_iterator, r) {
    SkBitmap bigBitmap;
    bigBitmap.allocN32Pixels(400, 400);
    SkBitmap bitmap;
    bigBitmap.extractSubset(&bitmap, {15, 25, 19, 35});
    for (int y = 0; y < bitmap.height(); ++y) {
        for (int x = 0; x < bitmap.width(); ++x) {
            *bitmap.getAddr32(x,y) = (uint32_t) (x * 0x100 + y);
        }
    }
    for (SkPixelIterator32::Pixel pixel: SkPixelIterator32(bitmap)) {
        if (0 == pixel.pt.x()) { SkDebugf("\n"); }
        SkDebugf("%d %d 0x%08X   ", pixel.pt.x(), pixel.pt.y(), *pixel.addr);
    }
}