Remove many unused files from //skia/ext

skia/ext/image_operations.cc

-// Copyright (c) 2012 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 <algorithm>
-#include <cmath>
-#include <limits>
-
-#include "skia/ext/image_operations.h"
-
-// TODO(pkasting): skia/ext should not depend on base/!
-#include "base/containers/stack_container.h"
-#include "base/logging.h"
-#include "base/metrics/histogram.h"
-#include "base/time/time.h"
-#include "base/trace_event/trace_event.h"
-#include "build/build_config.h"
-#include "skia/ext/convolver.h"
-#include "third_party/skia/include/core/SkColorPriv.h"
-#include "third_party/skia/include/core/SkRect.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:
-        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,
-                      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:
-        NOTREACHED();
-        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);
-
-  ComputeFilters(src_full_width, dest_subset.fLeft, dest_subset.width(),
-                 scale_x, &x_filter_);
-  ComputeFilters(src_full_height, dest_subset.fTop, dest_subset.height(),
-                 scale_y, &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,
-                                  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);
-
-  // This is how many source pixels from the center we need to count
-  // to support the filtering function.
-  float src_support = GetFilterSupport(clamped_scale) / clamped_scale;
-
-  // Speed up the divisions below by turning them into multiplies.
-  float inv_scale = 1.0f / scale;
-
-  base::StackVector<float, 64> filter_values;
-  base::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.
-    // 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;
-    }
-    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()));
-  }
-
-  output->PaddingForSIMD();
-}
-
-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,
-                                 SkBitmap::Allocator* allocator) {
-  TRACE_EVENT2("disabled-by-default-skia", "ImageOperations::Resize",
-               "src_pixels", source.width() * source.height(), "dst_pixels",
-               dest_width * dest_height);
-  // 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)));
-
-  // Time how long this takes to see if it's a problem for users.
-  base::TimeTicks resize_start = base::TimeTicks::Now();
-
-  SkIRect dest = { 0, 0, dest_width, dest_height };
-  DCHECK(dest.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_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() || source.colorType() != kN32_SkColorType)
-    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* source_subset =
-      reinterpret_cast<const uint8*>(source.getPixels());
-
-  // Convolve into the result.
-  SkBitmap result;
-  result.setInfo(SkImageInfo::MakeN32(dest_subset.width(), dest_subset.height(), source.alphaType()));
-  result.allocPixels(allocator, NULL);
-  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()),
-                 true);
-
-  base::TimeDelta delta = base::TimeTicks::Now() - resize_start;
-  UMA_HISTOGRAM_TIMES("Image.ResampleMS", delta);
-
-  return result;
-}
-
-// static
-SkBitmap ImageOperations::Resize(const SkBitmap& source,
-                                 ResizeMethod method,
-                                 int dest_width, int dest_height,
-                                 SkBitmap::Allocator* allocator) {
-  SkIRect dest_subset = { 0, 0, dest_width, dest_height };
-  return Resize(source, method, dest_width, dest_height, dest_subset,
-                allocator);
-}
-
-}  // namespace skia