The Tor Browser: gfx/2d/image_operations.cpp@97036ab72558 (annotated)

gfx/2d/image_operations.cpp@97036ab72558 (annotated)

gfx/2d/image_operations.cpp

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 // 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

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gfx/2d/image_operations.cpp@97036ab72558 (annotated)

gfx/2d/image_operations.cpp