GPU blit speedup: avoid texture filtering and texture domain when not necessary
BUG=crbug.com/102284
REVIEW=http://codereview.appspot.com/5836047/
TEST=code path already covered by gm/nocolorbleed gm/bitmapfilters and others
git-svn-id: http://skia.googlecode.com/svn/trunk@3421 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 2e82ad9..c8e5f48 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -55,6 +55,10 @@
// point we should probably get rid of these scaling constants and rebaseline
// all the blur tests.
#define BLUR_SIGMA_SCALE 0.6f
+// This constant represents the screen alignment criterion in texels for
+// requiring texture domain clamping to prevent color bleeding when drawing
+// a sub region of a larger source image.
+#define COLOR_BLEED_TOLERANCE SkFloatToScalar(0.001f)
///////////////////////////////////////////////////////////////////////////////
class SkGpuDevice::SkAutoCachedTexture : public ::SkNoncopyable {
@@ -1254,6 +1258,49 @@
}
}
+namespace {
+
+bool hasAlignedSamples(const SkRect& srcRect, const SkRect& transformedRect) {
+ // detect pixel disalignment
+ if (SkScalarAbs(SkScalarRoundToScalar(transformedRect.left()) -
+ transformedRect.left()) < COLOR_BLEED_TOLERANCE &&
+ SkScalarAbs(SkScalarRoundToScalar(transformedRect.top()) -
+ transformedRect.top()) < COLOR_BLEED_TOLERANCE &&
+ SkScalarAbs(transformedRect.width() - srcRect.width()) <
+ COLOR_BLEED_TOLERANCE &&
+ SkScalarAbs(transformedRect.height() - srcRect.height()) <
+ COLOR_BLEED_TOLERANCE) {
+ return true;
+ }
+ return false;
+}
+
+bool mayColorBleed(const SkRect& srcRect, const SkRect& transformedRect,
+ const SkMatrix& m) {
+ // Only gets called if hasAlignedSamples returned false.
+ // So we can assume that sampling is axis aligned but not texel aligned.
+ GrAssert(!hasAlignedSamples(srcRect, transformedRect));
+ SkRect innerSrcRect(srcRect), innerTransformedRect,
+ outerTransformedRect(transformedRect);
+ innerSrcRect.inset(SK_ScalarHalf, SK_ScalarHalf);
+ m.mapRect(&innerTransformedRect, innerSrcRect);
+
+ // The gap between outerTransformedRect and innerTransformedRect
+ // represents the projection of the source border area, which is
+ // problematic for color bleeding. We must check whether any
+ // destination pixels sample the border area.
+ outerTransformedRect.inset(COLOR_BLEED_TOLERANCE, COLOR_BLEED_TOLERANCE);
+ innerTransformedRect.outset(COLOR_BLEED_TOLERANCE, COLOR_BLEED_TOLERANCE);
+ SkIRect outer, inner;
+ outerTransformedRect.round(&outer);
+ innerTransformedRect.round(&inner);
+ // If the inner and outer rects round to the same result, it means the
+ // border does not overlap any pixel centers. Yay!
+ return inner != outer;
+}
+
+} // unnamed namespace
+
/*
* This is called by drawBitmap(), which has to handle images that may be too
* large to be represented by a single texture.
@@ -1300,11 +1347,35 @@
SkFloatToScalar(srcRect.fRight * wInv),
SkFloatToScalar(srcRect.fBottom * hInv));
- if (GrSamplerState::kNearest_Filter != sampler->getFilter() &&
- (srcRect.width() < bitmap.width() ||
- srcRect.height() < bitmap.height())) {
- // If drawing a subrect of the bitmap and filtering is enabled,
- // use a constrained texture domain to avoid color bleeding
+ bool needsTextureDomain = false;
+ if (GrSamplerState::kBilinear_Filter == sampler->getFilter())
+ {
+ // Need texture domain if drawing a sub rect.
+ needsTextureDomain = srcRect.width() < bitmap.width() ||
+ srcRect.height() < bitmap.height();
+ if (m.rectStaysRect() && draw.fMatrix->rectStaysRect()) {
+ // sampling is axis-aligned
+ GrRect floatSrcRect, transformedRect;
+ floatSrcRect.set(srcRect);
+ SkMatrix srcToDeviceMatrix(m);
+ srcToDeviceMatrix.postConcat(*draw.fMatrix);
+ srcToDeviceMatrix.mapRect(&transformedRect, floatSrcRect);
+
+ if (hasAlignedSamples(floatSrcRect, transformedRect)) {
+ // Samples are texel-aligned, so filtering is futile
+ sampler->setFilter(GrSamplerState::kNearest_Filter);
+ needsTextureDomain = false;
+ } else {
+ needsTextureDomain = needsTextureDomain &&
+ mayColorBleed(floatSrcRect, transformedRect, m);
+ }
+ }
+ }
+
+ GrRect textureDomain = GrRect::MakeEmpty();
+
+ if (needsTextureDomain) {
+ // Use a constrained texture domain to avoid color bleeding
GrScalar left, top, right, bottom;
if (srcRect.width() > 1) {
GrScalar border = GR_ScalarHalf / bitmap.width();
@@ -1320,10 +1391,9 @@
} else {
top = bottom = GrScalarHalf(paintRect.top() + paintRect.bottom());
}
- GrRect textureDomain;
- textureDomain.setLTRB(left, top, right, bottom);
- sampler->setTextureDomain(textureDomain);
+ textureDomain.setLTRB(left, top, right, bottom);
}
+ sampler->setTextureDomain(textureDomain);
fContext->drawRectToRect(*grPaint, dstRect, paintRect, &m);
}