Optional gradient dithering
Update raster gradient impls to observe the paint dithering flag.
For now this new behavior is disabled pending internal/external
client updates to mitigate diffs.
BUG=skia:4436
R=reed@google.com,mtklein@google.com,tomhudson@google.com
Review URL: https://codereview.chromium.org/1391303002
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index e25ec9e..88d650c 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -290,10 +290,17 @@
return true;
}
+#define SK_SUPPORT_LEGACY_GRADIENT_DITHERING
+
SkGradientShaderBase::GradientShaderBaseContext::GradientShaderBaseContext(
const SkGradientShaderBase& shader, const ContextRec& rec)
: INHERITED(shader, rec)
- , fCache(shader.refCache(getPaintAlpha()))
+#ifdef SK_SUPPORT_LEGACY_GRADIENT_DITHERING
+ , fDither(true)
+#else
+ , fDither(rec.fPaint->isDither())
+#endif
+ , fCache(shader.refCache(getPaintAlpha(), fDither))
{
const SkMatrix& inverse = this->getTotalInverse();
@@ -317,8 +324,9 @@
}
SkGradientShaderBase::GradientShaderCache::GradientShaderCache(
- U8CPU alpha, const SkGradientShaderBase& shader)
+ U8CPU alpha, bool dither, const SkGradientShaderBase& shader)
: fCacheAlpha(alpha)
+ , fCacheDither(dither)
, fShader(shader)
, fCache16Inited(false)
, fCache32Inited(false)
@@ -342,7 +350,7 @@
paint specifies a non-opaque alpha.
*/
void SkGradientShaderBase::GradientShaderCache::Build16bitCache(
- uint16_t cache[], SkColor c0, SkColor c1, int count) {
+ uint16_t cache[], SkColor c0, SkColor c1, int count, bool dither) {
SkASSERT(count > 1);
SkASSERT(SkColorGetA(c0) == 0xFF);
SkASSERT(SkColorGetA(c1) == 0xFF);
@@ -359,17 +367,31 @@
g = SkIntToFixed(g) + 0x8000;
b = SkIntToFixed(b) + 0x8000;
- do {
- unsigned rr = r >> 16;
- unsigned gg = g >> 16;
- unsigned bb = b >> 16;
- cache[0] = SkPackRGB16(SkR32ToR16(rr), SkG32ToG16(gg), SkB32ToB16(bb));
- cache[kCache16Count] = SkDitherPack888ToRGB16(rr, gg, bb);
- cache += 1;
- r += dr;
- g += dg;
- b += db;
- } while (--count != 0);
+ if (dither) {
+ do {
+ unsigned rr = r >> 16;
+ unsigned gg = g >> 16;
+ unsigned bb = b >> 16;
+ cache[0] = SkPackRGB16(SkR32ToR16(rr), SkG32ToG16(gg), SkB32ToB16(bb));
+ cache[kCache16Count] = SkDitherPack888ToRGB16(rr, gg, bb);
+ cache += 1;
+ r += dr;
+ g += dg;
+ b += db;
+ } while (--count != 0);
+ } else {
+ do {
+ unsigned rr = r >> 16;
+ unsigned gg = g >> 16;
+ unsigned bb = b >> 16;
+ cache[0] = SkPackRGB16(SkR32ToR16(rr), SkG32ToG16(gg), SkB32ToB16(bb));
+ cache[kCache16Count] = cache[0];
+ cache += 1;
+ r += dr;
+ g += dg;
+ b += db;
+ } while (--count != 0);
+ }
}
/*
@@ -392,7 +414,7 @@
void SkGradientShaderBase::GradientShaderCache::Build32bitCache(
SkPMColor cache[], SkColor c0, SkColor c1,
- int count, U8CPU paintAlpha, uint32_t gradFlags) {
+ int count, U8CPU paintAlpha, uint32_t gradFlags, bool dither) {
SkASSERT(count > 1);
// need to apply paintAlpha to our two endpoints
@@ -432,10 +454,15 @@
With this trick, we can add 0 for the first (no-op) and just adjust the
others.
*/
- SkUFixed a = SkIntToFixed(a0) + 0x2000;
- SkUFixed r = SkIntToFixed(r0) + 0x2000;
- SkUFixed g = SkIntToFixed(g0) + 0x2000;
- SkUFixed b = SkIntToFixed(b0) + 0x2000;
+ const SkUFixed bias0 = dither ? 0x2000 : 0x8000;
+ const SkUFixed bias1 = dither ? 0x8000 : 0;
+ const SkUFixed bias2 = dither ? 0xC000 : 0;
+ const SkUFixed bias3 = dither ? 0x4000 : 0;
+
+ SkUFixed a = SkIntToFixed(a0) + bias0;
+ SkUFixed r = SkIntToFixed(r0) + bias0;
+ SkUFixed g = SkIntToFixed(g0) + bias0;
+ SkUFixed b = SkIntToFixed(b0) + bias0;
/*
* Our dither-cell (spatially) is
@@ -450,18 +477,18 @@
if (0xFF == a0 && 0 == da) {
do {
- cache[kCache32Count*0] = SkPackARGB32(0xFF, (r + 0 ) >> 16,
- (g + 0 ) >> 16,
- (b + 0 ) >> 16);
- cache[kCache32Count*1] = SkPackARGB32(0xFF, (r + 0x8000) >> 16,
- (g + 0x8000) >> 16,
- (b + 0x8000) >> 16);
- cache[kCache32Count*2] = SkPackARGB32(0xFF, (r + 0xC000) >> 16,
- (g + 0xC000) >> 16,
- (b + 0xC000) >> 16);
- cache[kCache32Count*3] = SkPackARGB32(0xFF, (r + 0x4000) >> 16,
- (g + 0x4000) >> 16,
- (b + 0x4000) >> 16);
+ cache[kCache32Count*0] = SkPackARGB32(0xFF, (r + 0 ) >> 16,
+ (g + 0 ) >> 16,
+ (b + 0 ) >> 16);
+ cache[kCache32Count*1] = SkPackARGB32(0xFF, (r + bias1) >> 16,
+ (g + bias1) >> 16,
+ (b + bias1) >> 16);
+ cache[kCache32Count*2] = SkPackARGB32(0xFF, (r + bias2) >> 16,
+ (g + bias2) >> 16,
+ (b + bias2) >> 16);
+ cache[kCache32Count*3] = SkPackARGB32(0xFF, (r + bias3) >> 16,
+ (g + bias3) >> 16,
+ (b + bias3) >> 16);
cache += 1;
r += dr;
g += dg;
@@ -469,22 +496,22 @@
} while (--count != 0);
} else if (interpInPremul) {
do {
- cache[kCache32Count*0] = SkPackARGB32((a + 0 ) >> 16,
- (r + 0 ) >> 16,
- (g + 0 ) >> 16,
- (b + 0 ) >> 16);
- cache[kCache32Count*1] = SkPackARGB32((a + 0x8000) >> 16,
- (r + 0x8000) >> 16,
- (g + 0x8000) >> 16,
- (b + 0x8000) >> 16);
- cache[kCache32Count*2] = SkPackARGB32((a + 0xC000) >> 16,
- (r + 0xC000) >> 16,
- (g + 0xC000) >> 16,
- (b + 0xC000) >> 16);
- cache[kCache32Count*3] = SkPackARGB32((a + 0x4000) >> 16,
- (r + 0x4000) >> 16,
- (g + 0x4000) >> 16,
- (b + 0x4000) >> 16);
+ cache[kCache32Count*0] = SkPackARGB32((a + 0 ) >> 16,
+ (r + 0 ) >> 16,
+ (g + 0 ) >> 16,
+ (b + 0 ) >> 16);
+ cache[kCache32Count*1] = SkPackARGB32((a + bias1) >> 16,
+ (r + bias1) >> 16,
+ (g + bias1) >> 16,
+ (b + bias1) >> 16);
+ cache[kCache32Count*2] = SkPackARGB32((a + bias2) >> 16,
+ (r + bias2) >> 16,
+ (g + bias2) >> 16,
+ (b + bias2) >> 16);
+ cache[kCache32Count*3] = SkPackARGB32((a + bias3) >> 16,
+ (r + bias3) >> 16,
+ (g + bias3) >> 16,
+ (b + bias3) >> 16);
cache += 1;
a += da;
r += dr;
@@ -497,18 +524,18 @@
(r + 0 ) >> 16,
(g + 0 ) >> 16,
(b + 0 ) >> 16);
- cache[kCache32Count*1] = SkPremultiplyARGBInline((a + 0x8000) >> 16,
- (r + 0x8000) >> 16,
- (g + 0x8000) >> 16,
- (b + 0x8000) >> 16);
- cache[kCache32Count*2] = SkPremultiplyARGBInline((a + 0xC000) >> 16,
- (r + 0xC000) >> 16,
- (g + 0xC000) >> 16,
- (b + 0xC000) >> 16);
- cache[kCache32Count*3] = SkPremultiplyARGBInline((a + 0x4000) >> 16,
- (r + 0x4000) >> 16,
- (g + 0x4000) >> 16,
- (b + 0x4000) >> 16);
+ cache[kCache32Count*1] = SkPremultiplyARGBInline((a + bias1) >> 16,
+ (r + bias1) >> 16,
+ (g + bias1) >> 16,
+ (b + bias1) >> 16);
+ cache[kCache32Count*2] = SkPremultiplyARGBInline((a + bias2) >> 16,
+ (r + bias2) >> 16,
+ (g + bias2) >> 16,
+ (b + bias2) >> 16);
+ cache[kCache32Count*3] = SkPremultiplyARGBInline((a + bias3) >> 16,
+ (r + bias3) >> 16,
+ (g + bias3) >> 16,
+ (b + bias3) >> 16);
cache += 1;
a += da;
r += dr;
@@ -540,7 +567,7 @@
cache->fCache16 = cache->fCache16Storage;
if (cache->fShader.fColorCount == 2) {
Build16bitCache(cache->fCache16, cache->fShader.fOrigColors[0],
- cache->fShader.fOrigColors[1], kCache16Count);
+ cache->fShader.fOrigColors[1], kCache16Count, cache->fCacheDither);
} else {
Rec* rec = cache->fShader.fRecs;
int prevIndex = 0;
@@ -550,7 +577,8 @@
if (nextIndex > prevIndex)
Build16bitCache(cache->fCache16 + prevIndex, cache->fShader.fOrigColors[i-1],
- cache->fShader.fOrigColors[i], nextIndex - prevIndex + 1);
+ cache->fShader.fOrigColors[i], nextIndex - prevIndex + 1,
+ cache->fCacheDither);
prevIndex = nextIndex;
}
}
@@ -573,7 +601,7 @@
if (cache->fShader.fColorCount == 2) {
Build32bitCache(cache->fCache32, cache->fShader.fOrigColors[0],
cache->fShader.fOrigColors[1], kCache32Count, cache->fCacheAlpha,
- cache->fShader.fGradFlags);
+ cache->fShader.fGradFlags, cache->fCacheDither);
} else {
Rec* rec = cache->fShader.fRecs;
int prevIndex = 0;
@@ -584,7 +612,7 @@
if (nextIndex > prevIndex)
Build32bitCache(cache->fCache32 + prevIndex, cache->fShader.fOrigColors[i-1],
cache->fShader.fOrigColors[i], nextIndex - prevIndex + 1,
- cache->fCacheAlpha, cache->fShader.fGradFlags);
+ cache->fCacheAlpha, cache->fShader.fGradFlags, cache->fCacheDither);
prevIndex = nextIndex;
}
}
@@ -594,10 +622,11 @@
* The gradient holds a cache for the most recent value of alpha. Successive
* callers with the same alpha value will share the same cache.
*/
-SkGradientShaderBase::GradientShaderCache* SkGradientShaderBase::refCache(U8CPU alpha) const {
+SkGradientShaderBase::GradientShaderCache* SkGradientShaderBase::refCache(U8CPU alpha,
+ bool dither) const {
SkAutoMutexAcquire ama(fCacheMutex);
- if (!fCache || fCache->getAlpha() != alpha) {
- fCache.reset(new GradientShaderCache(alpha, *this));
+ if (!fCache || fCache->getAlpha() != alpha || fCache->getDither() != dither) {
+ fCache.reset(new GradientShaderCache(alpha, dither, *this));
}
// Increment the ref counter inside the mutex to ensure the returned pointer is still valid.
// Otherwise, the pointer may have been overwritten on a different thread before the object's
@@ -618,7 +647,7 @@
void SkGradientShaderBase::getGradientTableBitmap(SkBitmap* bitmap) const {
// our caller assumes no external alpha, so we ensure that our cache is
// built with 0xFF
- SkAutoTUnref<GradientShaderCache> cache(this->refCache(0xFF));
+ SkAutoTUnref<GradientShaderCache> cache(this->refCache(0xFF, true));
// build our key: [numColors + colors[] + {positions[]} + flags ]
int count = 1 + fColorCount + 1;
diff --git a/src/effects/gradients/SkGradientShaderPriv.h b/src/effects/gradients/SkGradientShaderPriv.h
index f6e80d9..01c53e8 100644
--- a/src/effects/gradients/SkGradientShaderPriv.h
+++ b/src/effects/gradients/SkGradientShaderPriv.h
@@ -126,7 +126,7 @@
// The cache is initialized on-demand when getCache16/32 is called.
class GradientShaderCache : public SkRefCnt {
public:
- GradientShaderCache(U8CPU alpha, const SkGradientShaderBase& shader);
+ GradientShaderCache(U8CPU alpha, bool dither, const SkGradientShaderBase& shader);
~GradientShaderCache();
const uint16_t* getCache16();
@@ -135,6 +135,7 @@
SkMallocPixelRef* getCache32PixelRef() const { return fCache32PixelRef; }
unsigned getAlpha() const { return fCacheAlpha; }
+ bool getDither() const { return fCacheDither; }
private:
// Working pointers. If either is nullptr, we need to recompute the corresponding cache values.
@@ -146,6 +147,7 @@
const unsigned fCacheAlpha; // The alpha value we used when we computed the cache.
// Larger than 8bits so we can store uninitialized
// value.
+ const bool fCacheDither; // The dither flag used when we computed the cache.
const SkGradientShaderBase& fShader;
@@ -156,9 +158,9 @@
static void initCache16(GradientShaderCache* cache);
static void initCache32(GradientShaderCache* cache);
- static void Build16bitCache(uint16_t[], SkColor c0, SkColor c1, int count);
+ static void Build16bitCache(uint16_t[], SkColor c0, SkColor c1, int count, bool dither);
static void Build32bitCache(SkPMColor[], SkColor c0, SkColor c1, int count,
- U8CPU alpha, uint32_t gradFlags);
+ U8CPU alpha, uint32_t gradFlags, bool dither);
};
class GradientShaderBaseContext : public SkShader::Context {
@@ -172,6 +174,7 @@
SkMatrix::MapXYProc fDstToIndexProc;
uint8_t fDstToIndexClass;
uint8_t fFlags;
+ bool fDither;
SkAutoTUnref<GradientShaderCache> fCache;
@@ -260,7 +263,7 @@
SkScalar* fOrigPos; // original positions
bool fColorsAreOpaque;
- GradientShaderCache* refCache(U8CPU alpha) const;
+ GradientShaderCache* refCache(U8CPU alpha, bool dither) const;
mutable SkMutex fCacheMutex;
mutable SkAutoTUnref<GradientShaderCache> fCache;