Support for color-spaces with multi-stop (texture) gradients

src/effects/gradients/SkGradientShader.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Sk4fLinearGradient.h"
 #include "SkGradientShaderPriv.h"
+#include "SkHalf.h"
 #include "SkLinearGradient.h"
 #include "SkRadialGradient.h"
 #include "SkTwoPointConicalGradient.h"
 #include "SkSweepGradient.h"
 
 void SkGradientShaderBase::Descriptor::flatten(SkWriteBuffer& buffer) const {
     buffer.writeColorArray(fColors, fCount);
     // TODO: Flatten fColors4f and fColorSpace
     if (fPos) {
         buffer.writeBool(true);
@@ skipping 517 matching lines @@
 
             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->fCacheDither);
             prevIndex = nextIndex;
         }
     }
 }
 
+void SkGradientShaderBase::initLinearBitmap(SkBitmap* bitmap) const {
+    const bool interpInPremul = SkToBool(fGradFlags &
+                                         SkGradientShader::kInterpolateColorsInPremul_Flag);
+    bitmap->lockPixels();
+    SkHalf* pixelsF16 = reinterpret_cast<SkHalf*>(bitmap->getPixels());
+    uint32_t* pixelsS32 = reinterpret_cast<uint32_t*>(bitmap->getPixels());
+
+    typedef std::function<void(const Sk4f&, int)> pixelWriteFn_t;
+
+    pixelWriteFn_t writeF16Pixel = [&](const Sk4f& x, int index) {
+        Sk4h c = SkFloatToHalf_finite_ftz(x);
+        pixelsF16[4*index+0] = c[0];
+        pixelsF16[4*index+1] = c[1];
+        pixelsF16[4*index+2] = c[2];
+        pixelsF16[4*index+3] = c[3];
+    };
+    pixelWriteFn_t writeS32Pixel = [&](const Sk4f& c, int index) {
+        pixelsS32[index] = Sk4f_toS32(c);
+    };
+
+    pixelWriteFn_t writeSizedPixel =
+        (kRGBA_F16_SkColorType == bitmap->colorType()) ? writeF16Pixel : writeS32Pixel;
+    pixelWriteFn_t writeUnpremulPixel = [&](const Sk4f& c, int index) {
+        writeSizedPixel(c * Sk4f(c[3], c[3], c[3], 1.0f), index);
+    };
+
+    pixelWriteFn_t writePixel = interpInPremul ? writeSizedPixel : writeUnpremulPixel;
+
+    int prevIndex = 0;
+    for (int i = 1; i < fColorCount; i++) {
+        int nextIndex = (fColorCount == 2) ? (kCache32Count - 1)
+            : SkFixedToFFFF(fRecs[i].fPos) >> kCache32Shift;
+        SkASSERT(nextIndex < kCache32Count);
+
+        if (nextIndex > prevIndex) {
+            Sk4f c0 = Sk4f::Load(fOrigColors4f[i - 1].vec());
+            Sk4f c1 = Sk4f::Load(fOrigColors4f[i].vec());
+            if (interpInPremul) {
+                c0 = c0 * Sk4f(c0[3], c0[3], c0[3], 1.0f);
+                c1 = c1 * Sk4f(c1[3], c1[3], c1[3], 1.0f);
+            }
+
+            Sk4f step = Sk4f(1.0f / static_cast<float>(nextIndex - prevIndex));
+            Sk4f delta = (c1 - c0) * step;
+
+            for (int curIndex = prevIndex; curIndex <= nextIndex; ++curIndex) {
+                writePixel(c0, curIndex);
+                c0 += delta;
+            }
+        }
+        prevIndex = nextIndex;
+    }
+    SkASSERT(prevIndex == kCache32Count - 1);
+    bitmap->unlockPixels();
+}
+
 /*
  *  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,
                                                                           bool dither) const {
     SkAutoMutexAcquire ama(fCacheMutex);
     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
     // ref count was incremented.
     fCache.get()->ref();
     return fCache;
 }
 
 SK_DECLARE_STATIC_MUTEX(gGradientCacheMutex);
 /*
  *  Because our caller might rebuild the same (logically the same) gradient
  *  over and over, we'd like to return exactly the same "bitmap" if possible,
  *  allowing the client to utilize a cache of our bitmap (e.g. with a GPU).
  *  To do that, we maintain a private cache of built-bitmaps, based on our
  *  colors and positions. Note: we don't try to flatten the fMapper, so if one
  *  is present, we skip the cache for now.
  */
-void SkGradientShaderBase::getGradientTableBitmap(SkBitmap* bitmap) const {
-    // our caller assumes no external alpha, so we ensure that our cache is
-    // built with 0xFF
+void SkGradientShaderBase::getGradientTableBitmap(SkBitmap* bitmap,
+                                                  GradientBitmapType bitmapType) const {
+    // our caller assumes no external alpha, so we ensure that our cache is built with 0xFF
     SkAutoTUnref<GradientShaderCache> cache(this->refCache(0xFF, true));
 
-    // build our key: [numColors + colors[] + {positions[]} + flags ]
-    int count = 1 + fColorCount + 1;
+    // build our key: [numColors + colors[] + {positions[]} + flags + colorType ]
+    int count = 1 + fColorCount + 1 + 1;
     if (fColorCount > 2) {
         count += fColorCount - 1;    // fRecs[].fPos
     }
 
     SkAutoSTMalloc<16, int32_t> storage(count);
     int32_t* buffer = storage.get();
 
     *buffer++ = fColorCount;
     memcpy(buffer, fOrigColors, fColorCount * sizeof(SkColor));
     buffer += fColorCount;
     if (fColorCount > 2) {
         for (int i = 1; i < fColorCount; i++) {
             *buffer++ = fRecs[i].fPos;
         }
     }
     *buffer++ = fGradFlags;
+    *buffer++ = static_cast<int32_t>(bitmapType);
     SkASSERT(buffer - storage.get() == count);
 
     ///////////////////////////////////
 
     static SkGradientBitmapCache* gCache;
-    // each cache cost 1K of RAM, since each bitmap will be 1x256 at 32bpp
+    // each cache cost 1K or 2K of RAM, since each bitmap will be 1x256 at either 32bpp or 64bpp
     static const int MAX_NUM_CACHED_GRADIENT_BITMAPS = 32;
     SkAutoMutexAcquire ama(gGradientCacheMutex);
 
     if (nullptr == gCache) {
         gCache = new SkGradientBitmapCache(MAX_NUM_CACHED_GRADIENT_BITMAPS);
     }
     size_t size = count * sizeof(int32_t);
 
     if (!gCache->find(storage.get(), size, bitmap)) {
-        // force our cahce32pixelref to be built
-        (void)cache->getCache32();
-        bitmap->setInfo(SkImageInfo::MakeN32Premul(kCache32Count, 1));
-        bitmap->setPixelRef(cache->getCache32PixelRef());
+        if (GradientBitmapType::kLegacy == bitmapType) {
+            // force our cache32pixelref to be built
+            (void)cache->getCache32();
+            bitmap->setInfo(SkImageInfo::MakeN32Premul(kCache32Count, 1));
+            bitmap->setPixelRef(cache->getCache32PixelRef());
+        } else {
+            // For these cases we use the bitmap cache, but not the GradientShaderCache. So just
+            // allocate and populate the bitmap's data directly.
 
+            SkImageInfo info;
+            switch (bitmapType) {
+                case GradientBitmapType::kSRGB:
+                    info = SkImageInfo::Make(kCache32Count, 1, kRGBA_8888_SkColorType,
+                                             kPremul_SkAlphaType,
+                                             SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named));
+                    break;
+                case GradientBitmapType::kHalfFloat:
+                    info = SkImageInfo::Make(kCache32Count, 1, kRGBA_F16_SkColorType,
+                                             kPremul_SkAlphaType,
+                                             SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named)
+                                                ->makeLinearGamma());
+                    break;
+                default:
+                    SkFAIL("Unexpected bitmap type");
+                    return;
+            }
+            bitmap->allocPixels(info);
+            this->initLinearBitmap(bitmap);
+        }
         gCache->add(storage.get(), size, *bitmap);
     }
 }
 
 void SkGradientShaderBase::commonAsAGradient(GradientInfo* info, bool flipGrad) const {
     if (info) {
         if (info->fColorCount >= fColorCount) {
             SkColor* colorLoc;
             Rec*     recLoc;
             if (flipGrad && (info->fColors || info->fColorOffsets)) {
@@ skipping 269 matching lines @@
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
 
 ///////////////////////////////////////////////////////////////////////////////
 
 #if SK_SUPPORT_GPU
 
 #include "GrContext.h"
 #include "GrInvariantOutput.h"
 #include "GrTextureStripAtlas.h"
 #include "gl/GrGLContext.h"
+#include "glsl/GrGLSLColorSpaceXformHelper.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "glsl/GrGLSLProgramDataManager.h"
 #include "glsl/GrGLSLUniformHandler.h"
 #include "SkGr.h"
 
 static inline bool close_to_one_half(const SkFixed& val) {
     return SkScalarNearlyEqual(SkFixedToScalar(val), SK_ScalarHalf);
 }
 
 static inline int color_type_to_color_count(GrGradientEffect::ColorType colorType) {
@@ skipping 191 matching lines @@
 
             break;
         }
 
         case GrGradientEffect::kTexture_ColorType: {
             SkScalar yCoord = e.getYCoord();
             if (yCoord != fCachedYCoord) {
                 pdman.set1f(fFSYUni, yCoord);
                 fCachedYCoord = yCoord;
             }
+            if (SkToBool(e.fColorSpaceXform)) {
+                pdman.setSkMatrix44(fColorSpaceXformUni, e.fColorSpaceXform->srcToDst());
+            }
             break;
         }
     }
 }
 
 uint32_t GrGradientEffect::GLSLProcessor::GenBaseGradientKey(const GrProcessor& processor) {
     const GrGradientEffect& e = processor.cast<GrGradientEffect>();
 
     uint32_t key = 0;
 
@@ skipping 17 matching lines @@
    
     if (SkShader::TileMode::kClamp_TileMode == e.fTileMode) {
         key |= kClampTileMode;
     } else if (SkShader::TileMode::kRepeat_TileMode == e.fTileMode) {
         key |= kRepeatTileMode;
     } else {
         key |= kMirrorTileMode;
     }
 #endif
 
+    key |= GrColorSpaceXform::XformKey(e.fColorSpaceXform.get()) << kReservedBits;
+
     return key;
 }
 
 void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBuilder,
                                                 GrGLSLUniformHandler* uniformHandler,
                                                 const GrGLSLCaps* glslCaps,
                                                 const GrGradientEffect& ge,
                                                 const char* gradientTValue,
                                                 const char* outputColor,
                                                 const char* inputColor,
@@ skipping 161 matching lines @@
                 fragBuilder->codeAppend("colorTemp.rgb *= colorTemp.a;");
             }
 
             fragBuilder->codeAppendf("%s = %s;", outputColor,
                                      (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
 
             break;
         }
 
         case kTexture_ColorType: {
+            GrGLSLColorSpaceXformHelper colorSpaceHelper(uniformHandler, ge.fColorSpaceXform.get(),
+                                                         &fColorSpaceXformUni);
+
             const char* fsyuni = uniformHandler->getUniformCStr(fFSYUni);
 
             fragBuilder->codeAppendf("vec2 coord = vec2(%s, %s);", gradientTValue, fsyuni);
             fragBuilder->codeAppendf("%s = ", outputColor);
-            fragBuilder->appendTextureLookupAndModulate(inputColor, texSamplers[0], "coord");
+            fragBuilder->appendTextureLookupAndModulate(inputColor, texSamplers[0], "coord",
+                                                        kVec2f_GrSLType, &colorSpaceHelper);
             fragBuilder->codeAppend(";");
 
             break;
         }
     }
 }
 
 /////////////////////////////////////////////////////////////////////
 
 GrGradientEffect::GrGradientEffect(const CreateArgs& args) {
     const SkGradientShaderBase& shader(*args.fShader);
 
     fIsOpaque = shader.isOpaque();
 
     fColorType = this->determineColorType(shader);
+    fColorSpaceXform = std::move(args.fColorSpaceXform);
 
     if (kTexture_ColorType != fColorType) {
         SkASSERT(shader.fOrigColors && shader.fOrigColors4f);
         if (args.fGammaCorrect) {
             fColors4f = SkTDArray<SkColor4f>(shader.fOrigColors4f, shader.fColorCount);
-            fColorSpaceXform = std::move(args.fColorSpaceXform);
         } else {
             fColors = SkTDArray<SkColor>(shader.fOrigColors, shader.fColorCount);
         }
 
 #if GR_GL_USE_ACCURATE_HARD_STOP_GRADIENTS
         if (shader.fOrigPos) {
             fPositions = SkTDArray<SkScalar>(shader.fOrigPos, shader.fColorCount);
         }
 #endif
     }
@@ skipping 20 matching lines @@
             }
 
             fCoordTransform.reset(kCoordSet, *args.fMatrix);
 
             break;
         case kTexture_ColorType:
             // doesn't matter how this is set, just be consistent because it is part of the
             // effect key.
             fPremulType = kBeforeInterp_PremulType;
 
+            SkGradientShaderBase::GradientBitmapType bitmapType =
+                SkGradientShaderBase::GradientBitmapType::kLegacy;
+            if (args.fGammaCorrect) {
+                // Try to use F16 if we can
+                if (args.fContext->caps()->isConfigTexturable(kRGBA_half_GrPixelConfig)) {
+                    bitmapType = SkGradientShaderBase::GradientBitmapType::kHalfFloat;
+                } else if (args.fContext->caps()->isConfigTexturable(kSRGBA_8888_GrPixelConfig)) {
+                    bitmapType = SkGradientShaderBase::GradientBitmapType::kSRGB;
+                } else {
+                    // This should never happen, but just fall back to legacy behavior
+                    SkASSERT("Requesting a gamma-correct gradient FP without F16 or sRGB");

[bsalomon, 2016/09/22 14:16:03]

Won't this string always be true?

I believe we use SkDEBUGFAIL for this purpose.

+                }
+            }
+
             SkBitmap bitmap;
-            shader.getGradientTableBitmap(&bitmap);
+            shader.getGradientTableBitmap(&bitmap, bitmapType);
 
             GrTextureStripAtlas::Desc desc;
             desc.fWidth  = bitmap.width();
             desc.fHeight = 32;
             desc.fRowHeight = bitmap.height();
             desc.fContext = args.fContext;
             desc.fConfig = SkImageInfo2GrPixelConfig(bitmap.info(), *args.fContext->caps());
             fAtlas = GrTextureStripAtlas::GetAtlas(desc);
             SkASSERT(fAtlas);
 
@@ skipping 96 matching lines @@
             (*stops)[i] = stop;
             stop = i < outColors - 1 ? stop + random->nextUScalar1() * (1.f - stop) : 1.f;
         }
     }
     *tm = static_cast<SkShader::TileMode>(random->nextULessThan(SkShader::kTileModeCount));
 
     return outColors;
 }
 
 #endif