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/*
* Copyright 2013 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkLumaColorFilter.h"
#include "SkColorPriv.h"
#include "SkString.h"
#if SK_SUPPORT_GPU
#include "gl/GrGLEffect.h"
#include "gl/GrGLShaderBuilder.h"
#include "GrContext.h"
#include "GrTBackendEffectFactory.h"
#endif
void SkLumaColorFilter::filterSpan(const SkPMColor src[], int count,
SkPMColor dst[]) const {
for (int i = 0; i < count; ++i) {
SkPMColor c = src[i];
/*
* While LuminanceToAlpha is defined to operate on un-premultiplied
* inputs, due to the final alpha scaling it can be computed based on
* premultipled components:
*
* LumA = (k1 * r / a + k2 * g / a + k3 * b / a) * a
* LumA = (k1 * r + k2 * g + k3 * b)
*/
unsigned luma = SkComputeLuminance(SkGetPackedR32(c),
SkGetPackedG32(c),
SkGetPackedB32(c));
dst[i] = SkPackARGB32(luma, 0, 0, 0);
}
}
SkColorFilter* SkLumaColorFilter::Create() {
return SkNEW(SkLumaColorFilter);
}
SkLumaColorFilter::SkLumaColorFilter() : INHERITED() {}
#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
SkLumaColorFilter::SkLumaColorFilter(SkReadBuffer& buffer) : INHERITED(buffer) {}
#endif
SkFlattenable* SkLumaColorFilter::CreateProc(SkReadBuffer&) {
return SkNEW(SkLumaColorFilter);
}
void SkLumaColorFilter::flatten(SkWriteBuffer&) const {}
#ifndef SK_IGNORE_TO_STRING
void SkLumaColorFilter::toString(SkString* str) const {
str->append("SkLumaColorFilter ");
}
#endif
#if SK_SUPPORT_GPU
class LumaColorFilterEffect : public GrEffect {
public:
static GrEffect* Create() {
GR_CREATE_STATIC_EFFECT(gLumaEffect, LumaColorFilterEffect, ());
return SkRef(gLumaEffect);
}
static const char* Name() { return "Luminance-to-Alpha"; }
virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE {
return GrTBackendEffectFactory<LumaColorFilterEffect>::getInstance();
}
virtual void getConstantColorComponents(GrColor* color,
uint32_t* validFlags) const SK_OVERRIDE {
// The output is always black.
*color = GrColorPackRGBA(0, 0, 0, GrColorUnpackA(*color));
*validFlags = kRGB_GrColorComponentFlags;
}
class GLEffect : public GrGLEffect {
public:
GLEffect(const GrBackendEffectFactory& factory,
const GrDrawEffect&)
: INHERITED(factory) {
}
static void GenKey(const GrDrawEffect&, const GrGLCaps&, GrEffectKeyBuilder* b) {}
virtual void emitCode(GrGLShaderBuilder* builder,
const GrDrawEffect&,
const GrEffectKey&,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray&) SK_OVERRIDE {
if (NULL == inputColor) {
inputColor = "vec4(1)";
}
builder->fsCodeAppendf("\tfloat luma = dot(vec3(%f, %f, %f), %s.rgb);\n",
SK_ITU_BT709_LUM_COEFF_R,
SK_ITU_BT709_LUM_COEFF_G,
SK_ITU_BT709_LUM_COEFF_B,
inputColor);
builder->fsCodeAppendf("\t%s = vec4(0, 0, 0, luma);\n",
outputColor);
}
private:
typedef GrGLEffect INHERITED;
};
private:
virtual bool onIsEqual(const GrEffect&) const SK_OVERRIDE {
return true;
}
};
GrEffect* SkLumaColorFilter::asNewEffect(GrContext*) const {
return LumaColorFilterEffect::Create();
}
#endif
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