Fast blurred rectangles on GPU

src/effects/SkBlurMaskFilter.cpp

Index: src/effects/SkBlurMaskFilter.cpp
diff --git a/src/effects/SkBlurMaskFilter.cpp b/src/effects/SkBlurMaskFilter.cpp
index d2c43d719bcd707ddd58a3adacfe27b6a1015476..e8a23e1873752ae4e3d155097d7819428c86b63f 100644
--- a/src/effects/SkBlurMaskFilter.cpp
+++ b/src/effects/SkBlurMaskFilter.cpp
@@ -19,7 +19,10 @@
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #include "GrTexture.h"
+#include "GrEffect.h"
+#include "gl/GrGLEffect.h"
 #include "effects/GrSimpleTextureEffect.h"
+#include "GrTBackendEffectFactory.h"
 #include "SkGrPixelRef.h"
 #endif
 
@@ -37,6 +40,11 @@ public:
                                   const SkIRect& clipBounds,
                                   const SkMatrix& ctm,
                                   SkRect* maskRect) const SK_OVERRIDE;
+    virtual bool directFilterMaskGPU(GrContext *context,
+                                     GrPaint *grp,
+                                     bool doFill,
+                                     SkPath *path) const SK_OVERRIDE;
+
     virtual bool filterMaskGPU(GrTexture* src,
                                const SkRect& maskRect,
                                GrTexture** result,
@@ -502,6 +510,257 @@ void SkBlurMaskFilterImpl::flatten(SkFlattenableWriteBuffer& buffer) const {
 
 #if SK_SUPPORT_GPU
 
+class GrGLRectBlurEffect;
+
+class GrRectBlurEffect : public GrEffect {
+public:
+    virtual ~GrRectBlurEffect();
+
+    static const char* Name() { return "RectBlur"; }
+
+    typedef GrGLRectBlurEffect GLEffect;
+
+    virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
+    virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
+
+    /**
+     * Create a simple filter effect with custom bicubic coefficients.
+     */
+    static GrEffectRef* Create(GrContext *context, unsigned int width, unsigned int height, 
+                               float sigma) {
+        GrTexture *horizontalScanline, *verticalScanline;
+        bool createdScanlines = CreateScanlineTextures(context, sigma, width, height,
+                                                       &horizontalScanline, &verticalScanline);
+        if (!createdScanlines) {
+            return NULL;
+        }
+        AutoEffectUnref effect(SkNEW_ARGS(GrRectBlurEffect, (width, height, sigma, 
+                                                             horizontalScanline, verticalScanline)));
+        return CreateEffectRef(effect);    
+    }
+    
+    unsigned int getWidth() const { return fWidth; }
+    unsigned int getHeight() const { return fHeight; }
+    unsigned int getSigma() const { return fSigma; }
+
+private:
+    GrRectBlurEffect(unsigned int width, unsigned int height, float sigma, 
+                     GrTexture *horizontal_scanline, GrTexture *vertical_scanline);
+    virtual bool onIsEqual(const GrEffect&) const SK_OVERRIDE;
+    
+    static bool CreateScanlineTextures(GrContext *context, float sigma,
+                                       unsigned int width, unsigned int height,
+                                       GrTexture **horizontalScanline,
+                                       GrTexture **verticalScanline);
+    
+    unsigned int fWidth, fHeight;
+    float fSigma;
+    GrTextureAccess  fHorizontalScanlineAccess;
+    GrTextureAccess  fVerticalScanlineAccess;
+    GrCoordTransform fTrivialTransform;
+
+    GR_DECLARE_EFFECT_TEST;
+
+    typedef GrEffect INHERITED;
+};
+
+class GrGLRectBlurEffect : public GrGLEffect {
+public:
+    GrGLRectBlurEffect(const GrBackendEffectFactory& factory,
+                      const GrDrawEffect&);
+    virtual void emitCode(GrGLShaderBuilder*,
+                          const GrDrawEffect&,
+                          EffectKey,
+                          const char* outputColor,
+                          const char* inputColor,
+                          const TransformedCoordsArray&,
+                          const TextureSamplerArray&) SK_OVERRIDE;
+
+    virtual void setData(const GrGLUniformManager&, const GrDrawEffect&) SK_OVERRIDE;
+
+private:
+    typedef GrGLUniformManager::UniformHandle        UniformHandle;
+
+    UniformHandle       fWidthUni;
+    UniformHandle       fHeightUni;
+
+    typedef GrGLEffect INHERITED;
+};
+
+GrGLRectBlurEffect::GrGLRectBlurEffect(const GrBackendEffectFactory& factory, const GrDrawEffect&)
+    : INHERITED(factory) {
+}
+
+void GrGLRectBlurEffect::emitCode(GrGLShaderBuilder* builder,
+                                 const GrDrawEffect&,
+                                 EffectKey key,
+                                 const char* outputColor,
+                                 const char* inputColor,
+                                 const TransformedCoordsArray& coords,
+                                 const TextureSamplerArray& samplers) {
+    
+    SkString texture_coords = builder->ensureFSCoords2D(coords, 0);
+    
+    builder->fsCodeAppendf("\tvec4 horiz = ");
+    builder->fsAppendTextureLookup( samplers[0], texture_coords.c_str() );
+    builder->fsCodeAppendf(";\n");
+    builder->fsCodeAppendf("\tvec4 vert = ");
+    builder->fsAppendTextureLookup( samplers[1], texture_coords.c_str() );
+    builder->fsCodeAppendf(";\n");
+    
+    builder->fsCodeAppendf("\tfloat final = (horiz*vert).r;\n");
+    builder->fsCodeAppendf("\t%s = final*%s;\n", outputColor, inputColor);

[bsalomon, 2013/12/21 02:50:09]

There is a weird case where inputColor may be NULL and the effect is supposed to
take that to mean solid white (yeah, very user-friendly).

There is a helper GrGLSLModulatef that skips the multiply when the input color
is NULL. There's an example here:
https://chromium.googlesource.com/external/skia/src/+/4ba644d7d0ae1a6eb097739...


There is a plan to fix this to make it less burdensome, but it will involve
changing the signature of emitCode unfortunately :(

+}
+
+void GrGLRectBlurEffect::setData(const GrGLUniformManager& uman,
+                                const GrDrawEffect& drawEffect) {
+}
+
+bool GrRectBlurEffect::CreateScanlineTextures(GrContext *context, float sigma,
+                                              unsigned int width, unsigned int height,
+                                              GrTexture **horizontalScanline,
+                                              GrTexture **verticalScanline) {
+    GrTextureParams params;
+    GrTextureDesc texDesc;
+    
+    unsigned int profile_size = 6*sigma;
+    
+    texDesc.fWidth = width;
+    texDesc.fHeight = 1;
+    texDesc.fConfig = kAlpha_8_GrPixelConfig;
+    
+    static const GrCacheID::Domain gBlurProfileDomain = GrCacheID::GenerateDomain();
+    GrCacheID::Key key;
+    memset(&key, 0, sizeof(key));
+    key.fData32[0] = profile_size;
+    key.fData32[1] = width;
+    key.fData32[2] = 1;
+    GrCacheID horizontalCacheID(gBlurProfileDomain, key);
+    
+    uint8_t *profile = NULL;
+    SkAutoTDeleteArray<uint8_t> ada(profile);
+    
+    *horizontalScanline = context->findAndRefTexture(texDesc, horizontalCacheID, &params);
+    
+    if (NULL == *horizontalScanline) {
+    
+        SkBlurMask::ComputeBlurProfile(sigma, &profile);
+        
+        SkAutoTMalloc<uint8_t> horizontalPixels(width);
+        SkBlurMask::ComputeBlurredScanline(horizontalPixels, profile, profile_size, width, sigma);
+    
+        *horizontalScanline = context->createTexture(&params, texDesc, horizontalCacheID, 
+                                                     horizontalPixels, 0);
+                                                     
+        if (NULL == *horizontalScanline) {
+            return false;
+        }
+    }
+    
+    texDesc.fWidth = 1;
+    texDesc.fHeight = height;
+    key.fData32[1] = 1;

[bsalomon, 2013/12/21 02:50:09]

This guy doesn't also need the profile size?

[humper, 2013/12/23 13:26:58]

He's already got it; I'm only overwriting the width and height (reusing the same
key data structure).

+    key.fData32[2] = height;
+    GrCacheID verticalCacheID(gBlurProfileDomain, key);
+    
+    *verticalScanline = context->findAndRefTexture(texDesc, verticalCacheID, &params);
+    if (NULL == *verticalScanline) {
+        if (NULL == profile) {
+            SkBlurMask::ComputeBlurProfile(sigma, &profile);
+        }
+        
+        SkAutoTMalloc<uint8_t> verticalPixels(height);
+        SkBlurMask::ComputeBlurredScanline(verticalPixels, profile, profile_size, height, sigma);
+    
+        *verticalScanline = context->createTexture(&params, texDesc, verticalCacheID, 
+                                                   verticalPixels, 0);
+                                                     
+        if (NULL == *verticalScanline) {
+            return false;
+        }
+        
+    }
+    return true;
+}
+
+GrRectBlurEffect::GrRectBlurEffect(unsigned int width, unsigned int height, float sigma,
+                                   GrTexture *horizontal_scanline, GrTexture *vertical_scanline)
+  : INHERITED(), 
+    fWidth(width),
+    fHeight(height),
+    fSigma(sigma),
+    fHorizontalScanlineAccess(horizontal_scanline),
+    fVerticalScanlineAccess(vertical_scanline),
+    fTrivialTransform(kLocal_GrCoordSet, SkMatrix()) {

[bsalomon, 2013/12/21 02:50:09]

I thought SkMatrix didn't have a default cons and we use SkMatrix::I() for the
identity, but maybe I'm wrong. Or does any matrix work here?

[humper, 2013/12/23 13:26:58]

Has to be the identity.  I believe that's the default, but I'll use ::I to make
it more explicit.

+    this->addTextureAccess(&fHorizontalScanlineAccess);  
+    this->addTextureAccess(&fVerticalScanlineAccess);  
+    this->addCoordTransform(&fTrivialTransform);
+}
+
+GrRectBlurEffect::~GrRectBlurEffect() {
+}
+
+const GrBackendEffectFactory& GrRectBlurEffect::getFactory() const {
+    return GrTBackendEffectFactory<GrRectBlurEffect>::getInstance();
+}
+
+bool GrRectBlurEffect::onIsEqual(const GrEffect& sBase) const {
+    const GrRectBlurEffect& s = CastEffect<GrRectBlurEffect>(sBase);
+    return this->getWidth() == s.getWidth() &&
+           this->getHeight() == s.getHeight() &&
+           this->getSigma() == s.getSigma();
+}
+
+void GrRectBlurEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {
+    // FIXME:  Perhaps we can do better.

[bsalomon, 2013/12/21 02:50:09]

I think this comment can be removed. It's not obvious to me that we can promise
anything useful about the output values from this effect. (This is used to help
optimize effects out of the shader or notice that blending can be disabled for a
program).

+    *validFlags = 0;
+    return;
+}
+
+GR_DEFINE_EFFECT_TEST(GrRectBlurEffect);
+
+GrEffectRef* GrRectBlurEffect::TestCreate(SkRandom* random,
+                                         GrContext* context,
+                                         const GrDrawTargetCaps&,
+                                         GrTexture**) {
+    float sigma = random->nextRangeF(3,8);
+    unsigned int width = random->nextRangeU(200,300);
+    unsigned int height = random->nextRangeU(200,300);
+    return GrRectBlurEffect::Create(context, width, height, sigma);
+}
+
+
+bool SkBlurMaskFilterImpl::directFilterMaskGPU(GrContext *context,
+                                               GrPaint *grp,
+                                               bool doFill,
+                                               SkPath *path) const {
+    GrContext::AutoMatrix am;
+    if (!am.setIdentity(context, grp)) {
+       return false;
+    }
+
+    SkRect rect;
+    if (!path->isRect(&rect)) {
+        return false;
+    }
+    
+    if (!doFill) {
+        return false;
+    }
+    
+    rect.outset(3*fSigma, 3*fSigma);
+    
+    SkAutoTUnref<GrEffectRef> effect(GrRectBlurEffect::Create(
+            context, rect.width(), rect.height(), fSigma));
+    if (!effect) {
+        return false;
+    }
+    grp->addCoverageEffect(effect);
+    
+    context->drawRectToRect(*grp, rect, SkRect::MakeWH(1,1));
+    return true;
+}
+
 bool SkBlurMaskFilterImpl::canFilterMaskGPU(const SkRect& srcBounds,
                                             const SkIRect& clipBounds,
                                             const SkMatrix& ctm,