diff -r 000000000000 -r 6474c204b198 gfx/2d/image_operations.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/2d/image_operations.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,552 @@
+// Copyright (c) 2006-2012 The Chromium Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+//  * Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+//  * Redistributions in binary form must reproduce the above copyright
+//    notice, this list of conditions and the following disclaimer in
+//    the documentation and/or other materials provided with the
+//    distribution.
+//  * Neither the name of Google, Inc. nor the names of its contributors
+//    may be used to endorse or promote products derived from this
+//    software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+// AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+// SUCH DAMAGE.
+
+#include "base/basictypes.h"
+
+#define _USE_MATH_DEFINES
+#include <algorithm>
+#include <cmath>
+#include <limits>
+
+#include "image_operations.h"
+
+#include "base/stack_container.h"
+#include "convolver.h"
+#include "skia/SkColorPriv.h"
+#include "skia/SkBitmap.h"
+#include "skia/SkRect.h"
+#include "skia/SkFontHost.h"
+
+namespace skia {
+
+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)
+}
+
+// Evaluates the Hamming filter of the given filter size window for the given
+// position.
+//
+// The filter covers [-filter_size, +filter_size]. Outside of this window
+// the value of the function is 0. Inside of the window, the value is sinus
+// cardinal multiplied by a recentered Hamming function. The traditional
+// Hamming formula for a window of size N and n ranging in [0, N-1] is:
+//   hamming(n) = 0.54 - 0.46 * cos(2 * pi * n / (N-1)))
+// In our case we want the function centered for x == 0 and at its minimum
+// on both ends of the window (x == +/- filter_size), hence the adjusted
+// formula:
+//   hamming(x) = (0.54 -
+//                 0.46 * cos(2 * pi * (x - filter_size)/ (2 * filter_size)))
+//              = 0.54 - 0.46 * cos(pi * x / filter_size - pi)
+//              = 0.54 + 0.46 * cos(pi * x / filter_size)
+float EvalHamming(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 sinc discontinuity at the origin.
+  const float xpi = x * static_cast<float>(M_PI);
+
+  return ((sin(xpi) / xpi) *  // sinc(x)
+          (0.54f + 0.46f * cos(xpi / filter_size)));  // hamming(x)
+}
+
+// ResizeFilter ----------------------------------------------------------------
+
+// Encapsulates computation and storage of the filters required for one complete
+// resize operation.
+class ResizeFilter {
+ public:
+  ResizeFilter(ImageOperations::ResizeMethod method,
+               int src_full_width, int src_full_height,
+               int dest_width, int dest_height,
+               const SkIRect& dest_subset);
+
+  // Returns the filled filter values.
+  const ConvolutionFilter1D& x_filter() { return x_filter_; }
+  const ConvolutionFilter1D& 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_HAMMING1:
+        // The Hamming filter takes as much space in the source image in
+        // each direction as the size of the window = 1 for Hamming1.
+        return 1.0f;
+      case ImageOperations::RESIZE_LANCZOS2:
+        // The Lanczos filter takes as much space in the source image in
+        // each direction as the size of the window = 2 for Lanczos2.
+        return 2.0f;
+      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:
+        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,
+                      ConvolutionFilter1D* 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_HAMMING1:
+        return EvalHamming(1, pos);
+      case ImageOperations::RESIZE_LANCZOS2:
+        return EvalLanczos(2, pos);
+      case ImageOperations::RESIZE_LANCZOS3:
+        return EvalLanczos(3, pos);
+      default:
+        return 0;
+    }
+  }
+
+  ImageOperations::ResizeMethod method_;
+
+  // 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.
+  SkIRect out_bounds_;
+
+  ConvolutionFilter1D x_filter_;
+  ConvolutionFilter1D y_filter_;
+
+  DISALLOW_COPY_AND_ASSIGN(ResizeFilter);
+};
+
+ResizeFilter::ResizeFilter(ImageOperations::ResizeMethod method,
+                           int src_full_width, int src_full_height,
+                           int dest_width, int dest_height,
+                           const SkIRect& dest_subset)
+    : method_(method),
+      out_bounds_(dest_subset) {
+  // method_ will only ever refer to an "algorithm method".
+  SkASSERT((ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
+           (method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD));
+
+  float scale_x = static_cast<float>(dest_width) /
+                  static_cast<float>(src_full_width);
+  float scale_y = static_cast<float>(dest_height) /
+                  static_cast<float>(src_full_height);
+
+  x_filter_support_ = GetFilterSupport(scale_x);
+  y_filter_support_ = GetFilterSupport(scale_y);
+
+  // 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_width, dest_subset.fLeft, dest_subset.width(),
+                 scale_x, src_x_support, &x_filter_);
+  ComputeFilters(src_full_height, dest_subset.fTop, dest_subset.height(),
+                 scale_y, src_y_support, &y_filter_);
+}
+
+// TODO(egouriou): Take advantage of periods in the convolution.
+// Practical resizing filters are periodic outside of the border area.
+// For Lanczos, a scaling by a (reduced) factor of p/q (q pixels in the
+// source become p pixels in the destination) will have a period of p.
+// A nice consequence is a period of 1 when downscaling by an integral
+// factor. Downscaling from typical display resolutions is also bound
+// to produce interesting periods as those are chosen to have multiple
+// small factors.
+// Small periods reduce computational load and improve cache usage if
+// the coefficients can be shared. For periods of 1 we can consider
+// loading the factors only once outside the borders.
+void ResizeFilter::ComputeFilters(int src_size,
+                                  int dest_subset_lo, int dest_subset_size,
+                                  float scale, float src_support,
+                                  ConvolutionFilter1D* 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_t, 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.
+    // Note that we base computations on the "center" of the pixels. To see
+    // why, observe that the destination pixel at coordinates (0, 0) in a 5.0x
+    // downscale should "cover" the pixels around the pixel with *its center*
+    // at coordinates (2.5, 2.5) in the source, not those around (0, 0).
+    // Hence we need to scale coordinates (0.5, 0.5), not (0, 0).
+    float src_pixel = (static_cast<float>(dest_subset_i) + 0.5f) * 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. We also need to consider the center of the pixel
+      // when comparing distance against 'src_pixel'. In the 5x downscale
+      // example used above the distance from the center of the filter to
+      // the pixel with coordinates (2, 2) should be 0, because its center
+      // is at (2.5, 2.5).
+      float src_filter_dist =
+           ((static_cast<float>(cur_filter_pixel) + 0.5f) - src_pixel);
+
+      // Since the filter really exists in dest space, map it there.
+      float dest_filter_dist = src_filter_dist * clamped_scale;
+
+      // Compute the filter value at that location.
+      float filter_value = ComputeFilter(dest_filter_dist);
+      filter_values->push_back(filter_value);
+
+      filter_sum += filter_value;
+    }
+
+    // The filter must be normalized so that we don't affect the brightness of
+    // the image. Convert to normalized fixed point.
+    int16_t fixed_sum = 0;
+    for (size_t i = 0; i < filter_values->size(); i++) {
+      int16_t 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_t 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()));
+  }
+
+  output->PaddingForSIMD(8);
+}
+
+ImageOperations::ResizeMethod ResizeMethodToAlgorithmMethod(
+    ImageOperations::ResizeMethod method) {
+  // Convert any "Quality Method" into an "Algorithm Method"
+  if (method >= ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD &&
+      method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD) {
+    return method;
+  }
+  // The call to ImageOperationsGtv::Resize() above took care of
+  // GPU-acceleration in the cases where it is possible. So now we just
+  // pick the appropriate software method for each resize quality.
+  switch (method) {
+    // Users of RESIZE_GOOD are willing to trade a lot of quality to
+    // get speed, allowing the use of linear resampling to get hardware
+    // acceleration (SRB). Hence any of our "good" software filters
+    // will be acceptable, and we use the fastest one, Hamming-1.
+    case ImageOperations::RESIZE_GOOD:
+      // Users of RESIZE_BETTER are willing to trade some quality in order
+      // to improve performance, but are guaranteed not to devolve to a linear
+      // resampling. In visual tests we see that Hamming-1 is not as good as
+      // Lanczos-2, however it is about 40% faster and Lanczos-2 itself is
+      // about 30% faster than Lanczos-3. The use of Hamming-1 has been deemed
+      // an acceptable trade-off between quality and speed.
+    case ImageOperations::RESIZE_BETTER:
+      return ImageOperations::RESIZE_HAMMING1;
+    default:
+      return ImageOperations::RESIZE_LANCZOS3;
+  }
+}
+
+}  // namespace
+
+// Resize ----------------------------------------------------------------------
+
+// static
+SkBitmap ImageOperations::Resize(const SkBitmap& source,
+                                 ResizeMethod method,
+                                 int dest_width, int dest_height,
+                                 const SkIRect& dest_subset,
+                                 void* dest_pixels /* = nullptr */) {
+  if (method == ImageOperations::RESIZE_SUBPIXEL)
+    return ResizeSubpixel(source, dest_width, dest_height, dest_subset);
+  else
+    return ResizeBasic(source, method, dest_width, dest_height, dest_subset,
+                       dest_pixels);
+}
+
+// static
+SkBitmap ImageOperations::ResizeSubpixel(const SkBitmap& source,
+                                         int dest_width, int dest_height,
+                                         const SkIRect& dest_subset) {
+  // Currently only works on Linux/BSD because these are the only platforms
+  // where SkFontHost::GetSubpixelOrder is defined.
+#if defined(XP_UNIX)
+  // Understand the display.
+  const SkFontHost::LCDOrder order = SkFontHost::GetSubpixelOrder();
+  const SkFontHost::LCDOrientation orientation =
+      SkFontHost::GetSubpixelOrientation();
+
+  // Decide on which dimension, if any, to deploy subpixel rendering.
+  int w = 1;
+  int h = 1;
+  switch (orientation) {
+    case SkFontHost::kHorizontal_LCDOrientation:
+      w = dest_width < source.width() ? 3 : 1;
+      break;
+    case SkFontHost::kVertical_LCDOrientation:
+      h = dest_height < source.height() ? 3 : 1;
+      break;
+  }
+
+  // Resize the image.
+  const int width = dest_width * w;
+  const int height = dest_height * h;
+  SkIRect subset = { dest_subset.fLeft, dest_subset.fTop,
+                     dest_subset.fLeft + dest_subset.width() * w,
+                     dest_subset.fTop + dest_subset.height() * h };
+  SkBitmap img = ResizeBasic(source, ImageOperations::RESIZE_LANCZOS3, width,
+                             height, subset);
+  const int row_words = img.rowBytes() / 4;
+  if (w == 1 && h == 1)
+    return img;
+
+  // Render into subpixels.
+  SkBitmap result;
+  result.setConfig(SkBitmap::kARGB_8888_Config, dest_subset.width(),
+                   dest_subset.height());
+  result.allocPixels();
+  if (!result.readyToDraw())
+    return img;
+
+  SkAutoLockPixels locker(img);
+  if (!img.readyToDraw())
+    return img;
+
+  uint32_t* src_row = img.getAddr32(0, 0);
+  uint32_t* dst_row = result.getAddr32(0, 0);
+  for (int y = 0; y < dest_subset.height(); y++) {
+    uint32_t* src = src_row;
+    uint32_t* dst = dst_row;
+    for (int x = 0; x < dest_subset.width(); x++, src += w, dst++) {
+      uint8_t r = 0, g = 0, b = 0, a = 0;
+      switch (order) {
+        case SkFontHost::kRGB_LCDOrder:
+          switch (orientation) {
+            case SkFontHost::kHorizontal_LCDOrientation:
+              r = SkGetPackedR32(src[0]);
+              g = SkGetPackedG32(src[1]);
+              b = SkGetPackedB32(src[2]);
+              a = SkGetPackedA32(src[1]);
+              break;
+            case SkFontHost::kVertical_LCDOrientation:
+              r = SkGetPackedR32(src[0 * row_words]);
+              g = SkGetPackedG32(src[1 * row_words]);
+              b = SkGetPackedB32(src[2 * row_words]);
+              a = SkGetPackedA32(src[1 * row_words]);
+              break;
+          }
+          break;
+        case SkFontHost::kBGR_LCDOrder:
+          switch (orientation) {
+            case SkFontHost::kHorizontal_LCDOrientation:
+              b = SkGetPackedB32(src[0]);
+              g = SkGetPackedG32(src[1]);
+              r = SkGetPackedR32(src[2]);
+              a = SkGetPackedA32(src[1]);
+              break;
+            case SkFontHost::kVertical_LCDOrientation:
+              b = SkGetPackedB32(src[0 * row_words]);
+              g = SkGetPackedG32(src[1 * row_words]);
+              r = SkGetPackedR32(src[2 * row_words]);
+              a = SkGetPackedA32(src[1 * row_words]);
+              break;
+          }
+          break;
+        case SkFontHost::kNONE_LCDOrder:
+          break;
+      }
+      // Premultiplied alpha is very fragile.
+      a = a > r ? a : r;
+      a = a > g ? a : g;
+      a = a > b ? a : b;
+      *dst = SkPackARGB32(a, r, g, b);
+    }
+    src_row += h * row_words;
+    dst_row += result.rowBytes() / 4;
+  }
+  result.setAlphaType(img.alphaType());
+  return result;
+#else
+  return SkBitmap();
+#endif  // OS_POSIX && !OS_MACOSX && !defined(OS_ANDROID)
+}
+
+// static
+SkBitmap ImageOperations::ResizeBasic(const SkBitmap& source,
+                                      ResizeMethod method,
+                                      int dest_width, int dest_height,
+                                      const SkIRect& dest_subset,
+                                      void* dest_pixels /* = nullptr */) {
+  // Ensure that the ResizeMethod enumeration is sound.
+  SkASSERT(((RESIZE_FIRST_QUALITY_METHOD <= method) &&
+            (method <= RESIZE_LAST_QUALITY_METHOD)) ||
+           ((RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
+            (method <= RESIZE_LAST_ALGORITHM_METHOD)));
+
+  // 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_width < 1 || dest_height < 1)
+    return SkBitmap();
+
+  method = ResizeMethodToAlgorithmMethod(method);
+  // Check that we deal with an "algorithm methods" from this point onward.
+  SkASSERT((ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
+           (method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD));
+
+  SkAutoLockPixels locker(source);
+  if (!source.readyToDraw())
+      return SkBitmap();
+
+  ResizeFilter filter(method, source.width(), source.height(),
+                      dest_width, dest_height, 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_t* source_subset =
+      reinterpret_cast<const uint8_t*>(source.getPixels());
+
+  // Convolve into the result.
+  SkBitmap result;
+  result.setConfig(SkBitmap::kARGB_8888_Config,
+                   dest_subset.width(), dest_subset.height());
+
+  if (dest_pixels) {
+    result.setPixels(dest_pixels);
+  } else {
+    result.allocPixels();
+  }
+
+  if (!result.readyToDraw())
+    return SkBitmap();
+
+  BGRAConvolve2D(source_subset, static_cast<int>(source.rowBytes()),
+                 !source.isOpaque(), filter.x_filter(), filter.y_filter(),
+                 static_cast<int>(result.rowBytes()),
+                 static_cast<unsigned char*>(result.getPixels()),
+                 /* sse = */ false);
+
+  // Preserve the "opaque" flag for use as an optimization later.
+  result.setAlphaType(source.alphaType());
+
+  return result;
+}
+
+// static
+SkBitmap ImageOperations::Resize(const SkBitmap& source,
+                                 ResizeMethod method,
+                                 int dest_width, int dest_height,
+                                 void* dest_pixels /* = nullptr */) {
+  SkIRect dest_subset = { 0, 0, dest_width, dest_height };
+  return Resize(source, method, dest_width, dest_height, dest_subset,
+                dest_pixels);
+}
+
+}  // namespace skia