void Image::drawPattern(GraphicsContext* context,
const FloatRect& floatSrcRect,
const AffineTransform& patternTransform,
const FloatPoint& phase,
ColorSpace styleColorSpace,
CompositeOperator compositeOp,
const FloatRect& destRect)
{
FloatRect normSrcRect = normalizeRect(floatSrcRect);
if (destRect.isEmpty() || normSrcRect.isEmpty())
return; // nothing to draw
NativeImageSkia* bitmap = nativeImageForCurrentFrame();
if (!bitmap)
return;
// This is a very inexpensive operation. It will generate a new bitmap but
// it will internally reference the old bitmap's pixels, adjusting the row
// stride so the extra pixels appear as padding to the subsetted bitmap.
SkBitmap srcSubset;
SkIRect srcRect = enclosingIntRect(normSrcRect);
bitmap->extractSubset(&srcSubset, srcRect);
SkBitmap resampled;
SkShader* shader;
// Figure out what size the bitmap will be in the destination. The
// destination rect is the bounds of the pattern, we need to use the
// matrix to see how bit it will be.
float destBitmapWidth, destBitmapHeight;
TransformDimensions(patternTransform, srcRect.width(), srcRect.height(),
&destBitmapWidth, &destBitmapHeight);
// Compute the resampling mode.
ResamplingMode resampling;
if (context->platformContext()->isPrinting())
resampling = RESAMPLE_LINEAR;
else {
resampling = computeResamplingMode(*bitmap,
srcRect.width(), srcRect.height(),
destBitmapWidth, destBitmapHeight);
}
// Load the transform WebKit requested.
SkMatrix matrix(patternTransform);
if (resampling == RESAMPLE_AWESOME) {
// Do nice resampling.
SkBitmap resampled = skia::ImageOperations::Resize(srcSubset,
skia::ImageOperations::RESIZE_LANCZOS3,
static_cast<int>(destBitmapWidth),
static_cast<int>(destBitmapHeight));
shader = SkShader::CreateBitmapShader(resampled, SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode);
// Since we just resized the bitmap, we need to undo the scale set in
// the image transform.
matrix.setScaleX(SkIntToScalar(1));
matrix.setScaleY(SkIntToScalar(1));
} else {
// No need to do nice resampling.
shader = SkShader::CreateBitmapShader(srcSubset, SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode);
}
// We also need to translate it such that the origin of the pattern is the
// origin of the destination rect, which is what WebKit expects. Skia uses
// the coordinate system origin as the base for the patter. If WebKit wants
// a shifted image, it will shift it from there using the patternTransform.
float adjustedX = phase.x() + normSrcRect.x() *
narrowPrecisionToFloat(patternTransform.a());
float adjustedY = phase.y() + normSrcRect.y() *
narrowPrecisionToFloat(patternTransform.d());
matrix.postTranslate(SkFloatToScalar(adjustedX),
SkFloatToScalar(adjustedY));
shader->setLocalMatrix(matrix);
SkPaint paint;
paint.setShader(shader)->unref();
paint.setXfermodeMode(WebCoreCompositeToSkiaComposite(compositeOp));
paint.setFilterBitmap(resampling == RESAMPLE_LINEAR);
context->platformContext()->paintSkPaint(destRect, paint);
}
// Draws the given bitmap to the given canvas. The subset of the source bitmap
// identified by src_rect is drawn to the given destination rect. The bitmap
// will be resampled to resample_width * resample_height (this is the size of
// the whole image, not the subset). See shouldResampleBitmap for more.
//
// This does a lot of computation to resample only the portion of the bitmap
// that will only be drawn. This is critical for performance since when we are
// scrolling, for example, we are only drawing a small strip of the image.
// Resampling the whole image every time is very slow, so this speeds up things
// dramatically.
static void drawResampledBitmap(SkCanvas& canvas, SkPaint& paint, const NativeImageSkia& bitmap, const SkIRect& srcIRect, const SkRect& destRect)
{
// First get the subset we need. This is efficient and does not copy pixels.
SkBitmap subset;
bitmap.extractSubset(&subset, srcIRect);
SkRect srcRect;
srcRect.set(srcIRect);
// Whether we're doing a subset or using the full source image.
bool srcIsFull = srcIRect.fLeft == 0 && srcIRect.fTop == 0
&& srcIRect.width() == bitmap.width()
&& srcIRect.height() == bitmap.height();
// We will always draw in integer sizes, so round the destination rect.
SkIRect destRectRounded;
destRect.round(&destRectRounded);
SkIRect resizedImageRect = // Represents the size of the resized image.
{ 0, 0, destRectRounded.width(), destRectRounded.height() };
if (srcIsFull && bitmap.hasResizedBitmap(destRectRounded.width(), destRectRounded.height())) {
// Yay, this bitmap frame already has a resized version.
SkBitmap resampled = bitmap.resizedBitmap(destRectRounded.width(), destRectRounded.height());
canvas.drawBitmapRect(resampled, 0, destRect, &paint);
return;
}
// Compute the visible portion of our rect.
SkRect destBitmapSubsetSk;
ClipRectToCanvas(canvas, destRect, &destBitmapSubsetSk);
destBitmapSubsetSk.offset(-destRect.fLeft, -destRect.fTop);
// The matrix inverting, etc. could have introduced rounding error which
// causes the bounds to be outside of the resized bitmap. We round outward
// so we always lean toward it being larger rather than smaller than we
// need, and then clamp to the bitmap bounds so we don't get any invalid
// data.
SkIRect destBitmapSubsetSkI;
destBitmapSubsetSk.roundOut(&destBitmapSubsetSkI);
if (!destBitmapSubsetSkI.intersect(resizedImageRect))
return; // Resized image does not intersect.
if (srcIsFull && bitmap.shouldCacheResampling(
resizedImageRect.width(),
resizedImageRect.height(),
destBitmapSubsetSkI.width(),
destBitmapSubsetSkI.height())) {
// We're supposed to resize the entire image and cache it, even though
// we don't need all of it.
SkBitmap resampled = bitmap.resizedBitmap(destRectRounded.width(),
destRectRounded.height());
canvas.drawBitmapRect(resampled, 0, destRect, &paint);
} else {
// We should only resize the exposed part of the bitmap to do the
// minimal possible work.
// Resample the needed part of the image.
SkBitmap resampled = skia::ImageOperations::Resize(subset,
skia::ImageOperations::RESIZE_LANCZOS3,
destRectRounded.width(), destRectRounded.height(),
destBitmapSubsetSkI);
// Compute where the new bitmap should be drawn. Since our new bitmap
// may be smaller than the original, we have to shift it over by the
// same amount that we cut off the top and left.
destBitmapSubsetSkI.offset(destRect.fLeft, destRect.fTop);
SkRect offsetDestRect;
offsetDestRect.set(destBitmapSubsetSkI);
canvas.drawBitmapRect(resampled, 0, offsetDestRect, &paint);
}
}
