text: // 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
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  // 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"
  
  #include <algorithm>
  #include <cmath>
  #include <limits>
  
  #include "image_operations.h"
  
  #include "base/stack_container.h"
  #include "convolver.h"
  #include "skia/include/core/SkColorPriv.h"
  #include "skia/include/core/SkBitmap.h"
  #include "skia/include/core/SkRect.h"
  #include "skia/include/core/SkFontHost.h"
  
  namespace skia {
  
  namespace resize {
  
  // 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 ComputeFilters(ImageOperations::ResizeMethod method,
                      int src_size, int dst_size,
                      int dest_subset_lo, int dest_subset_size,
                      ConvolutionFilter1D* output) {
    // method_ will only ever refer to an "algorithm method".
    SkASSERT((ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
             (method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD));
  
    float scale = static_cast<float>(dst_size) / static_cast<float>(src_size);
   
    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);
  
    float src_support = GetFilterSupport(method, clamped_scale) / clamped_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(method, 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);
  }
  
  } // namespace resize
  
  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;
    }
  }
  
  // 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;
    SkImageInfo info = SkImageInfo::Make(dest_subset.width(),
                                         dest_subset.height(),
                                         kBGRA_8888_SkColorType,
                                         kPremul_SkAlphaType);
  
  
    result.allocPixels(info);
    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();
  
    ConvolutionFilter1D x_filter;
    ConvolutionFilter1D y_filter;
  
    resize::ComputeFilters(method, source.width(), dest_width, dest_subset.fLeft, dest_subset.width(), &x_filter);
    resize::ComputeFilters(method, source.height(), dest_height, dest_subset.fTop, dest_subset.height(), &y_filter);
  
    // 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;
    SkImageInfo info = SkImageInfo::Make(dest_subset.width(),
                                         dest_subset.height(),
                                         kBGRA_8888_SkColorType,
                                         kPremul_SkAlphaType);
  
    if (dest_pixels) {
      result.installPixels(info, dest_pixels, info.minRowBytes());
    } else {
      result.allocPixels(info);
    }
  
    if (!result.readyToDraw())
      return SkBitmap();
  
    BGRAConvolve2D(source_subset, static_cast<int>(source.rowBytes()),
                   !source.isOpaque(), x_filter, y_filter,
                   static_cast<int>(result.rowBytes()),
                   static_cast<unsigned char*>(result.getPixels()));
  
    // 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
  