Implement SkXfermode image filter. This required changing the signature of SkXfermode::asNewEffectOrCoeffs(), to add an optional background texture.

For the raster path, we do a straightforward 2-pass method: draw background, then composite the foreground over it.

For the GPU path, if the xfermode can be expressed as an effect, we build an effect with the background texture incorporated, then do a single-pass draw fetching both foreground and background textures, and compositing to the result. If the xfermode is expressed as src/dst coefficients, we do a 2-pass draw as in the raster path and use fixed-function blending.

R=bsalomon@google.com, reed@google.com

Review URL: https://codereview.chromium.org/16125008

git-svn-id: http://skia.googlecode.com/svn/trunk@9373 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 49 insertions, 0 deletions

diff --git a/include/effects/SkXfermodeImageFilter.h b/include/effects/SkXfermodeImageFilter.h
new file mode 100644
index 0000000000..ec7ce87046
--- /dev/null
+++ b/include/effects/SkXfermodeImageFilter.h
@@ -0,0 +1,49 @@
+/*
+ * 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.
+ */
+
+#ifndef SkXfermodeImageFilter_DEFINED
+#define SkXfermodeImageFilter_DEFINED
+
+#include "SkImageFilter.h"
+
+class SkBitmap;
+class SkXfermode;
+
+class SK_API SkXfermodeImageFilter : public SkImageFilter {
+    /**
+     * This filter takes an xfermode, and uses it to composite the foreground
+     * over the background.  If foreground or background is NULL, the input
+     * bitmap (src) is used instead.
+      */
+
+public:
+    SkXfermodeImageFilter(SkXfermode* mode, SkImageFilter* background, SkImageFilter* foreground = NULL);
+
+    virtual ~SkXfermodeImageFilter();
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkXfermodeImageFilter)
+
+    virtual bool onFilterImage(Proxy* proxy,
+                               const SkBitmap& src,
+                               const SkMatrix& ctm,
+                               SkBitmap* dst,
+                               SkIPoint* offset) SK_OVERRIDE;
+#if SK_SUPPORT_GPU
+    virtual bool canFilterImageGPU() const SK_OVERRIDE { return true; }
+    virtual bool filterImageGPU(Proxy* proxy, const SkBitmap& src, SkBitmap* result) SK_OVERRIDE;
+#endif
+
+protected:
+    explicit SkXfermodeImageFilter(SkFlattenableReadBuffer& buffer);
+    virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
+
+private:
+    SkXfermode* fMode;
+    typedef SkImageFilter INHERITED;
+};
+
+#endif