Adding an option to render only the shadow in SkDropShadowImageFilter

src/effects/SkDropShadowImageFilter.cpp

 /*
  * 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 "SkDropShadowImageFilter.h"
 
 #include "SkBitmap.h"
 #include "SkBlurImageFilter.h"
 #include "SkCanvas.h"
 #include "SkColorMatrixFilter.h"
 #include "SkDevice.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 
 SkDropShadowImageFilter::SkDropShadowImageFilter(SkScalar dx, SkScalar dy,
                                                  SkScalar sigmaX, SkScalar sigmaY, SkColor color,
-                                                 SkImageFilter* input, const CropRect* cropRect,
-                                                 uint32_t uniqueID)
+                                                 ShadowMode shadowMode, SkImageFilter* input,
+                                                 const CropRect* cropRect, uint32_t uniqueID)
     : INHERITED(1, &input, cropRect, uniqueID)
     , fDx(dx)
     , fDy(dy)
     , fSigmaX(sigmaX)
     , fSigmaY(sigmaY)
     , fColor(color)
+    , fShadowMode(shadowMode)
 {
 }
 
 #ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
 SkDropShadowImageFilter::SkDropShadowImageFilter(SkReadBuffer& buffer)
  : INHERITED(1, buffer) {
     fDx = buffer.readScalar();
     fDy = buffer.readScalar();
     fSigmaX = buffer.readScalar();
     fSigmaY = buffer.readScalar();
     fColor = buffer.readColor();
+    fShadowMode = buffer.isVersionLT(SkReadBuffer::kDropShadowMode_Version) ?
+                  kDrawShadowAndForeground_ShadowMode :
+                  static_cast<ShadowMode>(buffer.readInt());
     buffer.validate(SkScalarIsFinite(fDx) &&
                     SkScalarIsFinite(fDy) &&
                     SkScalarIsFinite(fSigmaX) &&
                     SkScalarIsFinite(fSigmaY));
 }
 #endif
 
 SkFlattenable* SkDropShadowImageFilter::CreateProc(SkReadBuffer& buffer) {
     SK_IMAGEFILTER_UNFLATTEN_COMMON(common, 1);
     SkScalar dx = buffer.readScalar();
     SkScalar dy = buffer.readScalar();
     SkScalar sigmaX = buffer.readScalar();
     SkScalar sigmaY = buffer.readScalar();
     SkColor color = buffer.readColor();
-    return Create(dx, dy, sigmaX, sigmaY, color, common.getInput(0), &common.cropRect(), common.uniqueID());
+    ShadowMode shadowMode = buffer.isVersionLT(SkReadBuffer::kDropShadowMode_Version) ?
+                            kDrawShadowAndForeground_ShadowMode :
+                            static_cast<ShadowMode>(buffer.readInt());
+    return Create(dx, dy, sigmaX, sigmaY, color, shadowMode, common.getInput(0),
+                  &common.cropRect(), common.uniqueID());
 }
 
 void SkDropShadowImageFilter::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeScalar(fDx);
     buffer.writeScalar(fDy);
     buffer.writeScalar(fSigmaX);
     buffer.writeScalar(fSigmaY);
     buffer.writeColor(fColor);
+    buffer.writeInt(static_cast<int>(fShadowMode));
 }
 
 bool SkDropShadowImageFilter::onFilterImage(Proxy* proxy, const SkBitmap& source,
                                             const Context& ctx,
                                             SkBitmap* result, SkIPoint* offset) const
 {
     SkBitmap src = source;
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
     if (getInput(0) && !getInput(0)->filterImage(proxy, source, ctx, &src, &srcOffset))
         return false;
@@ skipping 18 matching lines @@
         SkColorFilter::CreateModeFilter(fColor, SkXfermode::kSrcIn_Mode));
     SkPaint paint;
     paint.setImageFilter(blurFilter.get());
     paint.setColorFilter(colorFilter.get());
     paint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
     SkVector offsetVec = SkVector::Make(fDx, fDy);
     ctx.ctm().mapVectors(&offsetVec, 1);
     canvas.translate(SkIntToScalar(srcOffset.fX - bounds.fLeft),
                      SkIntToScalar(srcOffset.fY - bounds.fTop));
     canvas.drawBitmap(src, offsetVec.fX, offsetVec.fY, &paint);
-    canvas.drawBitmap(src, 0, 0);
+    if (fShadowMode == kDrawShadowAndForeground_ShadowMode) {
+        canvas.drawBitmap(src, 0, 0);
+    }
     *result = device->accessBitmap(false);
     offset->fX = bounds.fLeft;
     offset->fY = bounds.fTop;
     return true;
 }
 
 void SkDropShadowImageFilter::computeFastBounds(const SkRect& src, SkRect* dst) const {
     if (getInput(0)) {
         getInput(0)->computeFastBounds(src, dst);
     } else {
         *dst = src;
     }
 
     SkRect shadowBounds = *dst;
     shadowBounds.offset(fDx, fDy);
     shadowBounds.outset(SkScalarMul(fSigmaX, SkIntToScalar(3)),
                         SkScalarMul(fSigmaY, SkIntToScalar(3)));
-    dst->join(shadowBounds);
+    if (fShadowMode == kDrawShadowAndForeground_ShadowMode) {
+        dst->join(shadowBounds);
+    } else {
+        *dst = shadowBounds;
+    }
 }
 
 bool SkDropShadowImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix& ctm,
                                              SkIRect* dst) const {
     SkIRect bounds = src;
     SkVector offsetVec = SkVector::Make(fDx, fDy);
     ctm.mapVectors(&offsetVec, 1);
     bounds.offset(-SkScalarCeilToInt(offsetVec.x()),
                   -SkScalarCeilToInt(offsetVec.y()));
     SkVector sigma = SkVector::Make(fSigmaX, fSigmaY);
     ctm.mapVectors(&sigma, 1);
     bounds.outset(SkScalarCeilToInt(SkScalarMul(sigma.x(), SkIntToScalar(3))),
                   SkScalarCeilToInt(SkScalarMul(sigma.y(), SkIntToScalar(3))));
-    bounds.join(src);
+    if (fShadowMode == kDrawShadowAndForeground_ShadowMode) {
+        bounds.join(src);
+    }
     if (getInput(0) && !getInput(0)->filterBounds(bounds, ctm, &bounds)) {
         return false;
     }
     *dst = bounds;
     return true;
 }