Image filters: implement offsets in GPU path.

src/effects/SkXfermodeImageFilter.cpp

 /*
  * Copyright 2013 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 "SkXfermodeImageFilter.h"
 #include "SkCanvas.h"
 #include "SkColorPriv.h"
 #include "SkFlattenableBuffers.h"
 #include "SkXfermode.h"
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #include "effects/GrSimpleTextureEffect.h"
 #include "SkGr.h"
 #include "SkImageFilterUtils.h"
 #endif
 
 ///////////////////////////////////////////////////////////////////////////////
 
-SkXfermodeImageFilter::SkXfermodeImageFilter(SkXfermode* mode, SkImageFilter* background, SkImageFilter* foreground)
+SkXfermodeImageFilter::SkXfermodeImageFilter(SkXfermode* mode,
+                                             SkImageFilter* background,
+                                             SkImageFilter* foreground)
   : INHERITED(background, foreground), fMode(mode) {
     SkSafeRef(fMode);
 }
 
 SkXfermodeImageFilter::~SkXfermodeImageFilter() {
     SkSafeUnref(fMode);
 }
 
 SkXfermodeImageFilter::SkXfermodeImageFilter(SkFlattenableReadBuffer& buffer)
   : INHERITED(buffer) {
     fMode = buffer.readFlattenableT<SkXfermode>();
 }
 
 void SkXfermodeImageFilter::flatten(SkFlattenableWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeFlattenable(fMode);
 }
 
 bool SkXfermodeImageFilter::onFilterImage(Proxy* proxy,
                                             const SkBitmap& src,
                                             const SkMatrix& ctm,
                                             SkBitmap* dst,
                                             SkIPoint* offset) {
     SkBitmap background = src, foreground = src;
     SkImageFilter* backgroundInput = getInput(0);
     SkImageFilter* foregroundInput = getInput(1);
-    if (backgroundInput && !backgroundInput->filterImage(proxy, src, ctm, &background, offset)) {
+    SkIPoint backgroundOffset = SkIPoint::Make(0, 0);
+    if (backgroundInput &&
+        !backgroundInput->filterImage(proxy, src, ctm, &background, &backgroundOffset)) {
         return false;
     }
-    if (foregroundInput && !foregroundInput->filterImage(proxy, src, ctm, &foreground, offset)) {
+    SkIPoint foregroundOffset = SkIPoint::Make(0, 0);
+    if (foregroundInput &&
+        !foregroundInput->filterImage(proxy, src, ctm, &foreground, &foregroundOffset)) {
         return false;
     }
     dst->setConfig(background.config(), background.width(), background.height());
     dst->allocPixels();
     SkCanvas canvas(*dst);
     SkPaint paint;
     paint.setXfermodeMode(SkXfermode::kSrc_Mode);
     canvas.drawBitmap(background, 0, 0, &paint);
     paint.setXfermode(fMode);
-    canvas.drawBitmap(foreground, 0, 0, &paint);
+    canvas.drawBitmap(foreground,
+                      SkIntToScalar(foregroundOffset.fX - backgroundOffset.fX),
+                      SkIntToScalar(foregroundOffset.fY - backgroundOffset.fY),
+                      &paint);
+    offset->fX += backgroundOffset.fX;
+    offset->fY += backgroundOffset.fY;
     return true;
 }
 
 #if SK_SUPPORT_GPU
 
-bool SkXfermodeImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, SkBitmap* result) {
+bool SkXfermodeImageFilter::filterImageGPU(Proxy* proxy,
+                                           const SkBitmap& src,
+                                           SkBitmap* result,
+                                           SkIPoint* offset) {
     SkBitmap background;
-    if (!SkImageFilterUtils::GetInputResultGPU(getInput(0), proxy, src, &background)) {
+    SkIPoint backgroundOffset = SkIPoint::Make(0, 0);
+    if (!SkImageFilterUtils::GetInputResultGPU(getInput(0), proxy, src, &background,
+                                               &backgroundOffset)) {
         return false;
     }
     GrTexture* backgroundTex = background.getTexture();
     SkBitmap foreground;
-    if (!SkImageFilterUtils::GetInputResultGPU(getInput(1), proxy, src, &foreground)) {
+    SkIPoint foregroundOffset = SkIPoint::Make(0, 0);
+    if (!SkImageFilterUtils::GetInputResultGPU(getInput(1), proxy, src, &foreground,
+                                               &foregroundOffset)) {
         return false;
     }
     GrTexture* foregroundTex = foreground.getTexture();
     GrContext* context = foregroundTex->getContext();
 
     GrEffectRef* xferEffect = NULL;
 
     GrTextureDesc desc;
     desc.fFlags = kRenderTarget_GrTextureFlagBit | kNoStencil_GrTextureFlagBit;
     desc.fWidth = src.width();
     desc.fHeight = src.height();
     desc.fConfig = kSkia8888_GrPixelConfig;
 
     GrAutoScratchTexture ast(context, desc);
     SkAutoTUnref<GrTexture> dst(ast.detach());
 
     GrContext::AutoRenderTarget art(context, dst->asRenderTarget());
 
     SkXfermode::Coeff sm, dm;
     if (!SkXfermode::AsNewEffectOrCoeff(fMode, context, &xferEffect, &sm, &dm, backgroundTex)) {
         return false;
     }
 
+    SkMatrix foregroundMatrix = GrEffect::MakeDivByTextureWHMatrix(foregroundTex);
+    foregroundMatrix.preTranslate(SkIntToScalar(backgroundOffset.fX-foregroundOffset.fX),
+                                  SkIntToScalar(backgroundOffset.fY-foregroundOffset.fY));
+
+
     GrPaint paint;
     SkRect srcRect;
     src.getBounds(&srcRect);
     if (NULL != xferEffect) {
         paint.colorStage(0)->setEffect(
-            GrSimpleTextureEffect::Create(foregroundTex, GrEffect::MakeDivByTextureWHMatrix(foregroundTex)))->unref();
+            GrSimpleTextureEffect::Create(foregroundTex, foregroundMatrix))->unref();
         paint.colorStage(1)->setEffect(xferEffect)->unref();
         context->drawRect(paint, srcRect);
     } else {
+        SkMatrix backgroundMatrix = GrEffect::MakeDivByTextureWHMatrix(backgroundTex);
         paint.colorStage(0)->setEffect(
-            GrSimpleTextureEffect::Create(backgroundTex, GrEffect::MakeDivByTextureWHMatrix(backgroundTex)))->unref();
+            GrSimpleTextureEffect::Create(backgroundTex, backgroundMatrix))->unref();
         context->drawRect(paint, srcRect);
         paint.setBlendFunc(sk_blend_to_grblend(sm), sk_blend_to_grblend(dm));
         paint.colorStage(0)->setEffect(
-            GrSimpleTextureEffect::Create(foregroundTex, GrEffect::MakeDivByTextureWHMatrix(foregroundTex)))->unref();
+            GrSimpleTextureEffect::Create(foregroundTex, foregroundMatrix))->unref();
         context->drawRect(paint, srcRect);
     }
+    offset->fX += backgroundOffset.fX;
+    offset->fY += backgroundOffset.fY;
     return SkImageFilterUtils::WrapTexture(dst, src.width(), src.height(), result);
 }
 
 #endif