Fold alpha to the draw in savelayer-draw-restore patterns with non-opaque draw
Fold alpha of a save layer call to the subsequent draw call paint, even when
the draw call paint color is already non-opaque.
Comparing the difference of the unoptimized and the optimized call pattern
with all (layer alpha, draw alpha) combinations, this produces
off-by-one pixels ~50% of the time.
Reduces layers of current desk_carsvg.skp (recorded with cross-process
picture image filters allowed) from 122 to 115.
BUG=skia:3119
Review URL: https://codereview.chromium.org/840483005
diff --git a/src/core/SkRecordOpts.cpp b/src/core/SkRecordOpts.cpp
index 7ab8054..df29b1b 100644
--- a/src/core/SkRecordOpts.cpp
+++ b/src/core/SkRecordOpts.cpp
@@ -106,14 +106,12 @@
const uint32_t layerColor = layerPaint->getColor();
const uint32_t drawColor = drawPaint->getColor();
- if (!IsOnlyAlpha(layerColor) || !IsOpaque(drawColor) ||
- HasAnyEffect(*layerPaint) || CantFoldAlpha(*drawPaint)) {
- // Too fancy for us. Actually, as long as layerColor is just an alpha
- // we can blend it into drawColor's alpha; drawColor doesn't strictly have to be opaque.
+ if (!IsOnlyAlpha(layerColor) || HasAnyEffect(*layerPaint) || CantFoldAlpha(*drawPaint)) {
+ // Too fancy for us.
return false;
}
- drawPaint->setColor(SkColorSetA(drawColor, SkColorGetA(layerColor)));
+ drawPaint->setAlpha(SkMulDiv255Round(SkColorGetA(drawColor), SkColorGetA(layerColor)));
return KillSaveLayerAndRestore(record, begin);
}
@@ -145,9 +143,6 @@
paint.getImageFilter();
}
- static bool IsOpaque(SkColor color) {
- return SkColorGetA(color) == SK_AlphaOPAQUE;
- }
static bool IsOnlyAlpha(SkColor color) {
return SK_ColorTRANSPARENT == SkColorSetA(color, SK_AlphaTRANSPARENT);
}
diff --git a/tests/RecordOptsTest.cpp b/tests/RecordOptsTest.cpp
index eaeb737..b6bfba4 100644
--- a/tests/RecordOptsTest.cpp
+++ b/tests/RecordOptsTest.cpp
@@ -118,50 +118,50 @@
SkRect bounds = SkRect::MakeWH(100, 200);
SkRect draw = SkRect::MakeWH(50, 60);
- SkPaint goodLayerPaint, badLayerPaint, worseLayerPaint;
- goodLayerPaint.setColor(0x03000000); // Only alpha.
- badLayerPaint.setColor( 0x03040506); // Not only alpha.
- worseLayerPaint.setXfermodeMode(SkXfermode::kDstIn_Mode); // Any effect will do.
+ SkPaint alphaOnlyLayerPaint, translucentLayerPaint, xfermodeLayerPaint;
+ alphaOnlyLayerPaint.setColor(0x03000000); // Only alpha.
+ translucentLayerPaint.setColor(0x03040506); // Not only alpha.
+ xfermodeLayerPaint.setXfermodeMode(SkXfermode::kDstIn_Mode); // Any effect will do.
- SkPaint goodDrawPaint, badDrawPaint;
- goodDrawPaint.setColor(0xFF020202); // Opaque.
- badDrawPaint.setColor( 0x0F020202); // Not opaque.
+ SkPaint opaqueDrawPaint, translucentDrawPaint;
+ opaqueDrawPaint.setColor(0xFF020202); // Opaque.
+ translucentDrawPaint.setColor(0x0F020202); // Not opaque.
// SaveLayer/Restore removed: No paint = no point.
recorder.saveLayer(NULL, NULL);
- recorder.drawRect(draw, goodDrawPaint);
+ recorder.drawRect(draw, opaqueDrawPaint);
recorder.restore();
assert_savelayer_restore(r, &record, 0, true);
// Bounds don't matter.
recorder.saveLayer(&bounds, NULL);
- recorder.drawRect(draw, goodDrawPaint);
+ recorder.drawRect(draw, opaqueDrawPaint);
recorder.restore();
assert_savelayer_restore(r, &record, 3, true);
// TODO(mtklein): test case with null draw paint
// No change: layer paint isn't alpha-only.
- recorder.saveLayer(NULL, &badLayerPaint);
- recorder.drawRect(draw, goodDrawPaint);
+ recorder.saveLayer(NULL, &translucentLayerPaint);
+ recorder.drawRect(draw, opaqueDrawPaint);
recorder.restore();
assert_savelayer_restore(r, &record, 6, false);
// No change: layer paint has an effect.
- recorder.saveLayer(NULL, &worseLayerPaint);
- recorder.drawRect(draw, goodDrawPaint);
+ recorder.saveLayer(NULL, &xfermodeLayerPaint);
+ recorder.drawRect(draw, opaqueDrawPaint);
recorder.restore();
assert_savelayer_restore(r, &record, 9, false);
- // No change: draw paint isn't opaque.
- recorder.saveLayer(NULL, &goodLayerPaint);
- recorder.drawRect(draw, badDrawPaint);
+ // SaveLayer/Restore removed: we can fold in the alpha!
+ recorder.saveLayer(NULL, &alphaOnlyLayerPaint);
+ recorder.drawRect(draw, translucentDrawPaint);
recorder.restore();
- assert_savelayer_restore(r, &record, 12, false);
+ assert_savelayer_restore(r, &record, 12, true);
// SaveLayer/Restore removed: we can fold in the alpha!
- recorder.saveLayer(NULL, &goodLayerPaint);
- recorder.drawRect(draw, goodDrawPaint);
+ recorder.saveLayer(NULL, &alphaOnlyLayerPaint);
+ recorder.drawRect(draw, opaqueDrawPaint);
recorder.restore();
assert_savelayer_restore(r, &record, 15, true);