skia/ext/image_operations.h

// 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.

#ifndef SKIA_EXT_IMAGE_OPERATIONS_H_
#define SKIA_EXT_IMAGE_OPERATIONS_H_

#include "base/basictypes.h"
#include "base/gfx/rect.h"
#include "skia/ext/skia_utils.h"
#include "third_party/skia/include/core/SkColor.h"

class SkBitmap;

namespace skia {

class ImageOperations {
 public:
  enum ResizeMethod {
    // Box filter. This is a weighted average of all of the pixels touching
    // the destination pixel. For enlargement, this is nearest neighbor.
    //
    // You probably don't want this, it is here for testing since it is easy to
    // compute. Use RESIZE_LANCZOS3 instead.
    RESIZE_BOX,

    // 3-cycle Lanczos filter. This is tall in the middle, goes negative on
    // each side, then oscillates 2 more times. It gives nice sharp edges.
    RESIZE_LANCZOS3,
  };

  // Resizes the given source bitmap using the specified resize method, so that
  // the entire image is (dest_size) big. The dest_subset is the rectangle in
  // this destination image that should actually be returned.
  //
  // The output image will be (dest_subset.width(), dest_subset.height()). This
  // will save work if you do not need the entire bitmap.
  //
  // The destination subset must be smaller than the destination image.
  static SkBitmap Resize(const SkBitmap& source,
                         ResizeMethod method,
                         int dest_width, int dest_height,
                         const gfx::Rect& dest_subset);

  // Alternate version for resizing and returning the entire bitmap rather than
  // a subset.
  static SkBitmap Resize(const SkBitmap& source,
                         ResizeMethod method,
                         int dest_width, int dest_height);

  // Create a bitmap that is a blend of two others. The alpha argument
  // specifies the opacity of the second bitmap. The provided bitmaps must
  // use have the kARGB_8888_Config config and be of equal dimensions.
  static SkBitmap CreateBlendedBitmap(const SkBitmap& first,
                                      const SkBitmap& second,
                                      double alpha);

  // Create a bitmap that is the original bitmap masked out by the mask defined
  // in the alpha bitmap. The images must use the kARGB_8888_Config config and
  // be of equal dimensions.
  static SkBitmap CreateMaskedBitmap(const SkBitmap& first,
                                     const SkBitmap& alpha);

  // We create a button background image by compositing the color and image
  // together, then applying the mask. This is a highly specialized composite
  // operation that is the equivalent of drawing a background in |color|,
  // tiling |image| over the top, and then masking the result out with |mask|.
  // The images must use kARGB_8888_Config config.
  static SkBitmap CreateButtonBackground(SkColor color,
                                         const SkBitmap& image,
                                         const SkBitmap& mask);

  // Blur a bitmap using an average-blur algorithm over the rectangle defined
  // by |blur_amount|. The blur will wrap around image edges.
  static SkBitmap CreateBlurredBitmap(const SkBitmap& bitmap, int blur_amount);

  // Shift a bitmap's HSL values. The shift values are in the range of 0-1,
  // with the option to specify -1 for 'no change'. The shift values are
  // defined as:
  // hsl_shift[0] (hue): The absolute hue value for the image - 0 and 1 map
  //    to 0 and 360 on the hue color wheel (red).
  // hsl_shift[1] (saturation): A saturation shift for the image, with the
  //    following key values:
  //    0 = remove all color.
  //    0.5 = leave unchanged.
  //    1 = fully saturate the image.
  // hsl_shift[2] (lightness): A lightness shift for the image, with the
  //    following key values:
  //    0 = remove all lightness (make all pixels black).
  //    0.5 = leave unchanged.
  //    1 = full lightness (make all pixels white).
  static SkBitmap CreateHSLShiftedBitmap(const SkBitmap& bitmap,
                                         HSL hsl_shift);

  // Create a bitmap that is cropped from another bitmap. This is special
  // because it tiles the original bitmap, so your coordinates can extend
  // outside the bounds of the original image.
  static SkBitmap CreateTiledBitmap(const SkBitmap& bitmap,
                                    int src_x, int src_y,
                                    int dst_w, int dst_h);

  // Makes a bitmap half has large in each direction by averaging groups of
  // 4 pixels. This is one step in generating a mipmap.
  static SkBitmap DownsampleByTwo(const SkBitmap& bitmap);

  // Iteratively downsamples by 2 until the bitmap is no smaller than the
  // input size. The normal use of this is to downsample the bitmap "close" to
  // the final size, and then use traditional resampling on the result.
  // Because the bitmap will be closer to the final size, it will be faster,
  // and linear interpolation will generally work well as a second step.
  static SkBitmap DownsampleByTwoUntilSize(const SkBitmap& bitmap,
                                           int min_w, int min_h);

 private:
  ImageOperations();  // Class for scoping only.
};

}  // namespace skia

#endif  // SKIA_EXT_IMAGE_OPERATIONS_H_