Implements a matrix convolution filter (raster path only). The filtering loop

is templated on the tiling mode for speed:  interior pixels are unconditionally
fetched; border pixels apply the appropriate tiling mode before fetching.  It
handles target, bias, divisor (as gain), and edge modes (named to be more
skia-like).  It does not handle the "preserveAlpha" semantics of
feConvolveMatrix, nor "kernelUnitLength".



git-svn-id: http://skia.googlecode.com/svn/trunk@5592 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 76 insertions, 0 deletions

diff --git a/include/effects/SkMatrixConvolutionImageFilter.h b/include/effects/SkMatrixConvolutionImageFilter.h
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+++ b/include/effects/SkMatrixConvolutionImageFilter.h
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+/*
+ * Copyright 2012 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 SkMatrixConvolutionImageFilter_DEFINED
+#define SkMatrixConvolutionImageFilter_DEFINED
+
+#include "SkSingleInputImageFilter.h"
+#include "SkScalar.h"
+#include "SkSize.h"
+#include "SkPoint.h"
+
+/*! \class SkMatrixConvolutionImageFilter
+    Matrix convolution image filter.  This filter applies an NxM image
+    processing kernel to a given input image.  This can be used to produce
+    effects such as sharpening, blurring, edge detection, etc.
+ */
+
+class SkMatrixConvolutionImageFilter : public SkSingleInputImageFilter {
+public:
+    /*! \enum TileMode */
+    enum TileMode {
+      kClamp_TileMode,         /*!< Clamp to the image's edge pixels. */
+      kRepeat_TileMode,        /*!< Wrap around to the image's opposite edge. */
+      kClampToBlack_TileMode,  /*!< Fill with transparent black. */
+    };
+
+    /** Construct a matrix convolution image filter.
+        @param kernelSize  The kernel size in pixels, in each dimension (N by M).
+        @param kernel      The image processing kernel.  Must contain N * M 
+                           elements, in row order.
+        @param gain        A scale factor applied to each pixel after
+                           convolution.  This can be used to normalize the
+                           kernel, if it does not sum to 1.
+        @param bias        A bias factor added to each pixel after convolution.
+        @param target      An offset applied to each pixel coordinate before
+                           convolution.  This can be used to center the kernel
+                           over the image (e.g., a 3x3 kernel should have a
+                           target of {1, 1}).
+        @param tileMode    How accesses outside the image are treated.  (@see
+                           TileMode).
+        @param input       The input image filter.  If NULL, the src bitmap
+                           passed to filterImage() is used instead.
+    */
+
+    SkMatrixConvolutionImageFilter(const SkISize& kernelSize, const SkScalar* kernel, SkScalar gain, SkScalar bias, const SkIPoint& target, TileMode tileMode, SkImageFilter* input = NULL);
+    virtual ~SkMatrixConvolutionImageFilter();
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkMatrixConvolutionImageFilter)
+
+protected:
+    SkMatrixConvolutionImageFilter(SkFlattenableReadBuffer& buffer);
+    virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
+
+    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
+                               SkBitmap* result, SkIPoint* loc) SK_OVERRIDE;
+
+private:
+    SkISize   fKernelSize;
+    SkScalar* fKernel;
+    SkScalar  fGain;
+    SkScalar  fBias;
+    SkIPoint  fTarget;
+    TileMode  fTileMode;
+    typedef SkSingleInputImageFilter INHERITED;
+
+    template <class PixelFetcher>
+    void filterPixels(const SkBitmap& src, SkBitmap* result, const SkIRect& rect);
+    void filterInteriorPixels(const SkBitmap& src, SkBitmap* result, const SkIRect& rect);
+    void filterBorderPixels(const SkBitmap& src, SkBitmap* result, const SkIRect& rect);
+};
+
+#endif