1 files changed, 169 insertions, 0 deletions
diff --git a/gfx/2d/SkConvolver.h b/gfx/2d/SkConvolver.h
new file mode 100644
index 0000000000..5ea8ab9b5d
--- /dev/null
+++ b/gfx/2d/SkConvolver.h
@@ -0,0 +1,169 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+// Copyright (c) 2011-2016 Google Inc.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the gfx/skia/LICENSE file.
+
+#ifndef MOZILLA_GFX_SKCONVOLVER_H_
+#define MOZILLA_GFX_SKCONVOLVER_H_
+
+#include "mozilla/Assertions.h"
+#include <cfloat>
+#include <cmath>
+#include <vector>
+
+namespace skia {
+
+class SkBitmapFilter {
+ public:
+  explicit SkBitmapFilter(float width) : fWidth(width) {}
+  virtual ~SkBitmapFilter() = default;
+
+  float width() const { return fWidth; }
+  virtual float evaluate(float x) const = 0;
+
+ protected:
+  float fWidth;
+};
+
+class SkBoxFilter final : public SkBitmapFilter {
+ public:
+  explicit SkBoxFilter(float width = 0.5f) : SkBitmapFilter(width) {}
+
+  float evaluate(float x) const override {
+    return (x >= -fWidth && x < fWidth) ? 1.0f : 0.0f;
+  }
+};
+
+class SkLanczosFilter final : public SkBitmapFilter {
+ public:
+  explicit SkLanczosFilter(float width = 3.0f) : SkBitmapFilter(width) {}
+
+  float evaluate(float x) const override {
+    if (x <= -fWidth || x >= fWidth) {
+      return 0.0f;  // Outside of the window.
+    }
+    if (x > -FLT_EPSILON && x < FLT_EPSILON) {
+      return 1.0f;  // Special case the discontinuity at the origin.
+    }
+    float xpi = x * float(M_PI);
+    return (sinf(xpi) / xpi) *                   // sinc(x)
+           sinf(xpi / fWidth) / (xpi / fWidth);  // sinc(x/fWidth)
+  }
+};
+
+// Represents a filter in one dimension. Each output pixel has one entry in this
+// object for the filter values contributing to it. You build up the filter
+// list by calling AddFilter for each output pixel (in order).
+//
+// We do 2-dimensional convolution by first convolving each row by one
+// SkConvolutionFilter1D, then convolving each column by another one.
+//
+// Entries are stored in ConvolutionFixed point, shifted left by kShiftBits.
+class SkConvolutionFilter1D {
+ public:
+  using ConvolutionFixed = short;
+
+  // The number of bits that ConvolutionFixed point values are shifted by.
+  enum { kShiftBits = 14 };
+
+  SkConvolutionFilter1D();
+  ~SkConvolutionFilter1D();
+
+  // Convert between floating point and our ConvolutionFixed point
+  // representation.
+  static ConvolutionFixed ToFixed(float f) {
+    return static_cast<ConvolutionFixed>(f * (1 << kShiftBits));
+  }
+
+  // Returns the maximum pixel span of a filter.
+  int maxFilter() const { return fMaxFilter; }
+
+  // Returns the number of filters in this filter. This is the dimension of the
+  // output image.
+  int numValues() const { return static_cast<int>(fFilters.size()); }
+
+  void reserveAdditional(int filterCount, int filterValueCount) {
+    fFilters.reserve(fFilters.size() + filterCount);
+    fFilterValues.reserve(fFilterValues.size() + filterValueCount);
+  }
+
+  // Appends the given list of scaling values for generating a given output
+  // pixel. |filterOffset| is the distance from the edge of the image to where
+  // the scaling factors start. The scaling factors apply to the source pixels
+  // starting from this position, and going for the next |filterLength| pixels.
+  //
+  // You will probably want to make sure your input is normalized (that is,
+  // all entries in |filterValuesg| sub to one) to prevent affecting the overall
+  // brighness of the image.
+  //
+  // The filterLength must be > 0.
+  void AddFilter(int filterOffset, const ConvolutionFixed* filterValues,
+                 int filterLength);
+
+  // Retrieves a filter for the given |valueOffset|, a position in the output
+  // image in the direction we're convolving. The offset and length of the
+  // filter values are put into the corresponding out arguments (see AddFilter
+  // above for what these mean), and a pointer to the first scaling factor is
+  // returned. There will be |filterLength| values in this array.
+  inline const ConvolutionFixed* FilterForValue(int valueOffset,
+                                                int* filterOffset,
+                                                int* filterLength) const {
+    const FilterInstance& filter = fFilters[valueOffset];
+    *filterOffset = filter.fOffset;
+    *filterLength = filter.fTrimmedLength;
+    if (filter.fTrimmedLength == 0) {
+      return nullptr;
+    }
+    return &fFilterValues[filter.fDataLocation];
+  }
+
+  bool ComputeFilterValues(const SkBitmapFilter& aBitmapFilter,
+                           int32_t aSrcSize, int32_t aDstSize);
+
+ private:
+  struct FilterInstance {
+    // Offset within filterValues for this instance of the filter.
+    int fDataLocation;
+
+    // Distance from the left of the filter to the center. IN PIXELS
+    int fOffset;
+
+    // Number of values in this filter instance.
+    int fTrimmedLength;
+
+    // Filter length as specified. Note that this may be different from
+    // 'trimmed_length' if leading/trailing zeros of the original floating
+    // point form were clipped differently on each tail.
+    int fLength;
+  };
+
+  // Stores the information for each filter added to this class.
+  std::vector<FilterInstance> fFilters;
+
+  // We store all the filter values in this flat list, indexed by
+  // |FilterInstance.data_location| to avoid the mallocs required for storing
+  // each one separately.
+  std::vector<ConvolutionFixed> fFilterValues;
+
+  // The maximum size of any filter we've added.
+  int fMaxFilter;
+};
+
+void convolve_horizontally(const unsigned char* srcData,
+                           const SkConvolutionFilter1D& filter,
+                           unsigned char* outRow, bool hasAlpha);
+
+void convolve_vertically(
+    const SkConvolutionFilter1D::ConvolutionFixed* filterValues,
+    int filterLength, unsigned char* const* sourceDataRows, int pixelWidth,
+    unsigned char* outRow, bool hasAlpha);
+
+bool BGRAConvolve2D(const unsigned char* sourceData, int sourceByteRowStride,
+                    bool sourceHasAlpha, const SkConvolutionFilter1D& filterX,
+                    const SkConvolutionFilter1D& filterY,
+                    int outputByteRowStride, unsigned char* output);
+
+}  // namespace skia
+
+#endif /* MOZILLA_GFX_SKCONVOLVER_H_ */