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Fold alpha to the draw in savelayer-draw-restore patterns with non-opaque draw

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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
This commit is contained in:
kkinnunen 2015-01-16 05:04:36 -08:00 committed by Commit bot
parent c695e95417
commit 678c1b019a
2 changed files with 22 additions and 27 deletions
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11
src/core/SkRecordOpts.cpp
View File

@ -106,14 +106,12 @@ struct SaveLayerDrawRestoreNooper {
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 @@ struct SaveLayerDrawRestoreNooper {
paint.getImageFilter();
}
static bool IsOpaque(SkColor color) {
return SkColorGetA(color) == SK_AlphaOPAQUE;
}
static bool IsOnlyAlpha(SkColor color) {
return SK_ColorTRANSPARENT == SkColorSetA(color, SK_AlphaTRANSPARENT);
}

38
tests/RecordOptsTest.cpp
View File

@ -118,50 +118,50 @@ DEF_TEST(RecordOpts_NoopSaveLayerDrawRestore, r) {
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);