1 files changed, 362 insertions, 0 deletions
diff --git a/base/gfx/image_operations.cc b/base/gfx/image_operations.cc
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+++ b/base/gfx/image_operations.cc
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+// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+#define _USE_MATH_DEFINES
+#include <cmath>
+#include <limits>
+#include <vector>
+
+#include "base/gfx/image_operations.h"
+
+#include "base/gfx/convolver.h"
+#include "base/gfx/rect.h"
+#include "base/gfx/size.h"
+#include "base/logging.h"
+#include "base/stack_container.h"
+#include "SkBitmap.h"
+
+namespace gfx {
+
+namespace {
+
+// Returns the ceiling/floor as an integer.
+inline int CeilInt(float val) {
+  return static_cast<int>(ceil(val));
+}
+inline int FloorInt(float val) {
+  return static_cast<int>(floor(val));
+}
+
+// Filter function computation -------------------------------------------------
+
+// Evaluates the box filter, which goes from -0.5 to +0.5.
+float EvalBox(float x) {
+  return (x >= -0.5f && x < 0.5f) ? 1.0f : 0.0f;
+}
+
+// Evaluates the Lanczos filter of the given filter size window for the given
+// position.
+//
+// |filter_size| is the width of the filter (the "window"), outside of which
+// the value of the function is 0. Inside of the window, the value is the
+// normalized sinc function:
+//   lanczos(x) = sinc(x) * sinc(x / filter_size);
+// where
+//   sinc(x) = sin(pi*x) / (pi*x);
+float EvalLanczos(int filter_size, float x) {
+  if (x <= -filter_size || x >= filter_size)
+    return 0.0f;  // Outside of the window.
+  if (x > -std::numeric_limits<float>::epsilon() &&
+      x < std::numeric_limits<float>::epsilon())
+    return 1.0f;  // Special case the discontinuity at the origin.
+  float xpi = x * static_cast<float>(M_PI);
+  return (sin(xpi) / xpi) *  // sinc(x)
+          sin(xpi / filter_size) / (xpi / filter_size);  // sinc(x/filter_size)
+}
+
+// ResizeFilter ----------------------------------------------------------------
+
+// Encapsulates computation and storage of the filters required for one complete
+// resize operation.
+class ResizeFilter {
+ public:
+  ResizeFilter(ImageOperations::ResizeMethod method,
+               const Size& src_full_size,
+               const Size& dest_size,
+               const Rect& dest_subset);
+
+  // Returns the bounds in the input bitmap of data that is used in the output.
+  // The filter offsets are within this rectangle.
+  const Rect& src_depend() { return src_depend_; }
+
+  // Returns the filled filter values.
+  const ConvolusionFilter1D& x_filter() { return x_filter_; }
+  const ConvolusionFilter1D& y_filter() { return y_filter_; }
+
+ private:
+  // Returns the number of pixels that the filer spans, in filter space (the
+  // destination image).
+  float GetFilterSupport(float scale) {
+    switch (method_) {
+      case ImageOperations::RESIZE_BOX:
+        // The box filter just scales with the image scaling.
+        return 0.5f;  // Only want one side of the filter = /2.
+      case ImageOperations::RESIZE_LANCZOS3:
+        // The lanczos filter takes as much space in the source image in
+        // each direction as the size of the window = 3 for Lanczos3.
+        return 3.0f;
+      default:
+        NOTREACHED();
+        return 1.0f;
+    }
+  }
+
+  // Computes one set of filters either horizontally or vertically. The caller
+  // will specify the "min" and "max" rather than the bottom/top and
+  // right/bottom so that the same code can be re-used in each dimension.
+  //
+  // |src_depend_lo| and |src_depend_size| gives the range for the source
+  // depend rectangle (horizontally or vertically at the caller's discretion
+  // -- see above for what this means).
+  //
+  // Likewise, the range of destination values to compute and the scale factor
+  // for the transform is also specified.
+  void ComputeFilters(int src_size,
+                      int dest_subset_lo, int dest_subset_size,
+                      float scale, float src_support,
+                      ConvolusionFilter1D* output);
+
+  // Computes the filter value given the coordinate in filter space.
+  inline float ComputeFilter(float pos) {
+    switch (method_) {
+      case ImageOperations::RESIZE_BOX:
+        return EvalBox(pos);
+      case ImageOperations::RESIZE_LANCZOS3:
+        return EvalLanczos(3, pos);
+      default:
+        NOTREACHED();
+        return 0;
+    }
+  }
+
+  ImageOperations::ResizeMethod method_;
+
+  // Subset of source the filters will touch.
+  Rect src_depend_;
+
+  // Size of the filter support on one side only in the destination space.
+  // See GetFilterSupport.
+  float x_filter_support_;
+  float y_filter_support_;
+
+  // Subset of scaled destination bitmap to compute.
+  Rect out_bounds_;
+
+  ConvolusionFilter1D x_filter_;
+  ConvolusionFilter1D y_filter_;
+
+  DISALLOW_EVIL_CONSTRUCTORS(ResizeFilter);
+};
+
+ResizeFilter::ResizeFilter(ImageOperations::ResizeMethod method,
+                           const Size& src_full_size,
+                           const Size& dest_size,
+                           const Rect& dest_subset)
+    : method_(method),
+      out_bounds_(dest_subset) {
+  float scale_x = static_cast<float>(dest_size.width()) /
+                  static_cast<float>(src_full_size.width());
+  float scale_y = static_cast<float>(dest_size.height()) /
+                  static_cast<float>(src_full_size.height());
+
+  x_filter_support_ = GetFilterSupport(scale_x);
+  y_filter_support_ = GetFilterSupport(scale_y);
+
+  gfx::Rect src_full(0, 0, src_full_size.width(), src_full_size.height());
+  gfx::Rect dest_full(0, 0,
+                      static_cast<int>(src_full_size.width() * scale_x + 0.5),
+                      static_cast<int>(src_full_size.height() * scale_y + 0.5));
+
+  // Support of the filter in source space.
+  float src_x_support = x_filter_support_ / scale_x;
+  float src_y_support = y_filter_support_ / scale_y;
+
+  ComputeFilters(src_full_size.width(), dest_subset.x(), dest_subset.width(),
+                 scale_x, src_x_support, &x_filter_);
+  ComputeFilters(src_full_size.height(), dest_subset.y(), dest_subset.height(),
+                 scale_y, src_y_support, &y_filter_);
+}
+
+void ResizeFilter::ComputeFilters(int src_size,
+                                  int dest_subset_lo, int dest_subset_size,
+                                  float scale, float src_support,
+                                  ConvolusionFilter1D* output) {
+  int dest_subset_hi = dest_subset_lo + dest_subset_size;  // [lo, hi)
+
+  // When we're doing a magnification, the scale will be larger than one. This
+  // means the destination pixels are much smaller than the source pixels, and
+  // that the range covered by the filter won't necessarily cover any source
+  // pixel boundaries. Therefore, we use these clamped values (max of 1) for
+  // some computations.
+  float clamped_scale = std::min(1.0f, scale);
+
+  // Speed up the divisions below by turning them into multiplies.
+  float inv_scale = 1.0f / scale;
+
+  StackVector<float, 64> filter_values;
+  StackVector<int16, 64> fixed_filter_values;
+
+  // Loop over all pixels in the output range. We will generate one set of
+  // filter values for each one. Those values will tell us how to blend the
+  // source pixels to compute the destination pixel.
+  for (int dest_subset_i = dest_subset_lo; dest_subset_i < dest_subset_hi;
+       dest_subset_i++) {
+    // Reset the arrays. We don't declare them inside so they can re-use the
+    // same malloc-ed buffer.
+    filter_values->clear();
+    fixed_filter_values->clear();
+
+    // This is the pixel in the source directly under the pixel in the dest.
+    float src_pixel = dest_subset_i * inv_scale;
+
+    // Compute the (inclusive) range of source pixels the filter covers.
+    int src_begin = std::max(0, FloorInt(src_pixel - src_support));
+    int src_end = std::min(src_size - 1, CeilInt(src_pixel + src_support));
+
+    // Compute the unnormalized filter value at each location of the source
+    // it covers.
+    float filter_sum = 0.0f;  // Sub of the filter values for normalizing.
+    for (int cur_filter_pixel = src_begin; cur_filter_pixel <= src_end;
+         cur_filter_pixel++) {
+      // Distance from the center of the filter, this is the filter coordinate
+      // in source space.
+      float src_filter_pos = cur_filter_pixel - src_pixel;
+
+      // Since the filter really exists in dest space, map it there.
+      float dest_filter_pos = src_filter_pos * clamped_scale;
+
+      // Compute the filter value at that location.
+      float filter_value = ComputeFilter(dest_filter_pos);
+      filter_values->push_back(filter_value);
+
+      filter_sum += filter_value;
+    }
+    DCHECK(!filter_values->empty()) << "We should always get a filter!";
+
+    // The filter must be normalized so that we don't affect the brightness of
+    // the image. Convert to normalized fixed point.
+    int16 fixed_sum = 0;
+    for (size_t i = 0; i < filter_values->size(); i++) {
+      int16 cur_fixed = output->FloatToFixed(filter_values[i] / filter_sum);
+      fixed_sum += cur_fixed;
+      fixed_filter_values->push_back(cur_fixed);
+    }
+
+    // The conversion to fixed point will leave some rounding errors, which
+    // we add back in to avoid affecting the brightness of the image. We
+    // arbitrarily add this to the center of the filter array (this won't always
+    // be the center of the filter function since it could get clipped on the
+    // edges, but it doesn't matter enough to worry about that case).
+    int16 leftovers = output->FloatToFixed(1.0f) - fixed_sum;
+    fixed_filter_values[fixed_filter_values->size() / 2] += leftovers;
+
+    // Now it's ready to go.
+    output->AddFilter(src_begin, &fixed_filter_values[0],
+                      static_cast<int>(fixed_filter_values->size()));
+  }
+}
+
+}  // namespace
+
+// Resize ----------------------------------------------------------------------
+
+// static
+SkBitmap ImageOperations::Resize(const SkBitmap& source,
+                                 ResizeMethod method,
+                                 const Size& dest_size,
+                                 const Rect& dest_subset) {
+  DCHECK(Rect(dest_size.width(), dest_size.height()).Contains(dest_subset)) <<
+      "The supplied subset does not fall within the destination image.";
+
+  // If the size of source or destination is 0, i.e. 0x0, 0xN or Nx0, just
+  // return empty
+  if (source.width() < 1 || source.height() < 1 ||
+      dest_size.width() < 1 || dest_size.height() < 1)
+      return SkBitmap();
+
+  SkAutoLockPixels locker(source);
+
+  ResizeFilter filter(method, Size(source.width(), source.height()),
+                      dest_size, dest_subset);
+
+  // Get a source bitmap encompassing this touched area. We construct the
+  // offsets and row strides such that it looks like a new bitmap, while
+  // referring to the old data.
+  const uint8* source_subset =
+      reinterpret_cast<const uint8*>(source.getPixels());
+
+  // Convolve into the result.
+  SkBitmap result;
+  result.setConfig(SkBitmap::kARGB_8888_Config,
+                   dest_subset.width(), dest_subset.height());
+  result.allocPixels();
+  BGRAConvolve2D(source_subset, static_cast<int>(source.rowBytes()),
+                 !source.isOpaque(), filter.x_filter(), filter.y_filter(),
+                 static_cast<unsigned char*>(result.getPixels()));
+
+  // Preserve the "opaque" flag for use as an optimization later.
+  result.setIsOpaque(source.isOpaque());
+
+  return result;
+}
+
+// static
+SkBitmap ImageOperations::Resize(const SkBitmap& source,
+                                 ResizeMethod method,
+                                 const Size& dest_size) {
+  Rect dest_subset(0, 0, dest_size.width(), dest_size.height());
+  return Resize(source, method, dest_size, dest_subset);
+}
+
+// static
+SkBitmap ImageOperations::CreateBlendedBitmap(const SkBitmap& first,
+                                              const SkBitmap& second,
+                                              double alpha) {
+  DCHECK(alpha <= 1 && alpha >= 0);
+  DCHECK(first.width() == second.width());
+  DCHECK(first.height() == second.height());
+  DCHECK(first.bytesPerPixel() == second.bytesPerPixel());
+  DCHECK(first.config() == SkBitmap::kARGB_8888_Config);
+
+  // Optimize for case where we won't need to blend anything.
+  static const double alpha_min = 1.0 / 255;
+  static const double alpha_max = 254.0 / 255;
+  if (alpha < alpha_min) {
+    return first;
+  } else if (alpha > alpha_max) {
+    return second;
+  }
+
+  SkAutoLockPixels lock_first(first);
+  SkAutoLockPixels lock_second(second);
+
+  SkBitmap blended;
+  blended.setConfig(SkBitmap::kARGB_8888_Config, first.width(),
+                    first.height(), 0);
+  blended.allocPixels();
+  blended.eraseARGB(0, 0, 0, 0);
+
+  double first_alpha = 1 - alpha;
+
+  for (int y = 0; y < first.height(); y++) {
+    uint32* first_row = first.getAddr32(0, y);
+    uint32* second_row = second.getAddr32(0, y);
+    uint32* dst_row = blended.getAddr32(0, y);
+
+    for (int x = 0; x < first.width(); x++) {
+      uint32 first_pixel = first_row[x];
+      uint32 second_pixel = second_row[x];
+
+      int a = static_cast<int>(
+          SkColorGetA(first_pixel) * first_alpha +
+          SkColorGetA(second_pixel) * alpha);
+      int r = static_cast<int>(
+          SkColorGetR(first_pixel) * first_alpha +
+          SkColorGetR(second_pixel) * alpha);
+      int g = static_cast<int>(
+          SkColorGetG(first_pixel) * first_alpha +
+          SkColorGetG(second_pixel) * alpha);
+      int b = static_cast<int>(
+          SkColorGetB(first_pixel) * first_alpha +
+          SkColorGetB(second_pixel) * alpha);
+
+      dst_row[x] = SkColorSetARGB(a, r, g, b);
+    }
+  }
+
+  return blended;
+}
+
+}  // namespace gfx
+