String ImageBuffer::toDataURL(const String& mimeType, const double* quality) const
{
    SkDevice* device = context()->platformContext()->canvas()->getDevice();
    SkBitmap bitmap = device->accessBitmap(false);

    // if we can't see the pixels directly, call readPixels() to get a copy.
    // this could happen if the device is backed by a GPU.
    bitmap.lockPixels(); // balanced by our destructor, or explicitly if getPixels() fails
    if (!bitmap.getPixels()) {
        bitmap.unlockPixels();
        SkIRect bounds = SkIRect::MakeWH(device->width(), device->height());
        if (!device->readPixels(bounds, &bitmap))
            return "data:,";
    }

    return ImageToDataURL(bitmap, mimeType, quality);
}
PassRefPtr<ByteArray> getImageData(const IntRect& rect, SkDevice& srcDevice,
                                   const IntSize& size)
{
    RefPtr<ByteArray> result = ByteArray::create(rect.width() * rect.height() * 4);

    SkBitmap::Config srcConfig = srcDevice.accessBitmap(false).config();

    if (srcConfig == SkBitmap::kNo_Config) {
        // This is an empty SkBitmap that could not be configured.
        ASSERT(!size.width() || !size.height());
        return result.release();
    }

    unsigned char* data = result->data();

    if (rect.x() < 0
        || rect.y() < 0
        || rect.maxX() > size.width()
        || rect.maxY() > size.height())
        memset(data, 0, result->length());

    int originX = rect.x();
    int destX = 0;
    if (originX < 0) {
        destX = -originX;
        originX = 0;
    }
    int endX = rect.maxX();
    if (endX > size.width())
        endX = size.width();
    int numColumns = endX - originX;

    if (numColumns <= 0)
        return result.release();

    int originY = rect.y();
    int destY = 0;
    if (originY < 0) {
        destY = -originY;
        originY = 0;
    }
    int endY = rect.maxY();
    if (endY > size.height())
        endY = size.height();
    int numRows = endY - originY;

    if (numRows <= 0)
        return result.release();

    ASSERT(srcConfig == SkBitmap::kARGB_8888_Config);

    unsigned destBytesPerRow = 4 * rect.width();

    SkBitmap srcBitmap;
    srcDevice.readPixels(SkIRect::MakeXYWH(originX, originY, numColumns, numRows), &srcBitmap);

    unsigned char* destRow = data + destY * destBytesPerRow + destX * 4;

    // Do conversion of byte order and alpha divide (if necessary)
    for (int y = 0; y < numRows; ++y) {
        SkPMColor* srcBitmapRow = srcBitmap.getAddr32(0, y);
        for (int x = 0; x < numColumns; ++x) {
            SkPMColor srcPMColor = srcBitmapRow[x];
            unsigned char* destPixel = &destRow[x * 4];
            if (multiplied == Unmultiplied) {
                unsigned char a = SkGetPackedA32(srcPMColor);
                destPixel[0] = a ? SkGetPackedR32(srcPMColor) * 255 / a : 0;
                destPixel[1] = a ? SkGetPackedG32(srcPMColor) * 255 / a : 0;
                destPixel[2] = a ? SkGetPackedB32(srcPMColor) * 255 / a : 0;
                destPixel[3] = a;
            } else {
                // Input and output are both pre-multiplied, we just need to re-arrange the
                // bytes from the bitmap format to RGBA.
                destPixel[0] = SkGetPackedR32(srcPMColor);
                destPixel[1] = SkGetPackedG32(srcPMColor);
                destPixel[2] = SkGetPackedB32(srcPMColor);
                destPixel[3] = SkGetPackedA32(srcPMColor);
            }
        }
        destRow += destBytesPerRow;
    }

    return result.release();
}