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// Copyright (c) 2011 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.
#include "third_party/skia/include/core/SkBitmap.h"
#include "third_party/skia/include/core/SkTypes.h"
struct SkIRect;
namespace skia {
class SK_API ImageOperations {
enum ResizeMethod {
// Quality Methods
// Those enumeration values express a desired quality/speed tradeoff.
// They are translated into an algorithm-specific method that depends
// on the capabilities (CPU, GPU) of the underlying platform.
// It is possible for all three methods to be mapped to the same
// algorithm on a given platform.
// Good quality resizing. Fastest resizing with acceptable visual quality.
// This is typically intended for use during interactive layouts
// where slower platforms may want to trade image quality for large
// increase in resizing performance.
// For example the resizing implementation may devolve to linear
// filtering if this enables GPU acceleration to be used.
// Note that the underlying resizing method may be determined
// on the fly based on the parameters for a given resize call.
// For example an implementation using a GPU-based linear filter
// in the common case may still use a higher-quality software-based
// filter in cases where using the GPU would actually be slower - due
// to too much latency - or impossible - due to image format or size
// constraints.
// Medium quality resizing. Close to high quality resizing (better
// than linear interpolation) with potentially some quality being
// traded-off for additional speed compared to RESIZE_BEST.
// This is intended, for example, for generation of large thumbnails
// (hundreds of pixels in each dimension) from large sources, where
// a linear filter would produce too many artifacts but where
// a RESIZE_HIGH might be too costly time-wise.
// High quality resizing. The algorithm is picked to favor image quality.
// Algorithm-specific enumerations
// 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.
// 1-cycle Hamming filter. This is tall is the middle and falls off towards
// the window edges but without going to 0. This is about 40% faster than
// a 2-cycle Lanczos.
// 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.
// enum aliases for first and last methods by algorithm or by quality.
// 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 SkIRect& dest_subset,
SkBitmap::Allocator* allocator = NULL);
// 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,
SkBitmap::Allocator* allocator = NULL);
ImageOperations(); // Class for scoping only.
} // namespace skia