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* Copyright 2013 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkBitmapScaler_DEFINED
#define SkBitmapScaler_DEFINED
#include "SkBitmap.h"
#include "SkConvolver.h"
/** \class SkBitmapScaler
Provides the interface for high quality image resampling.
class SK_API SkBitmapScaler {
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.
// enum aliases for first and last methods by algorithm or by quality.
static bool Resize(SkBitmap* result,
const SkBitmap& source,
ResizeMethod method,
float dest_width, float dest_height,
SkBitmap::Allocator* allocator = NULL);
static SkBitmap Resize(const SkBitmap& source,
ResizeMethod method,
float dest_width, float dest_height,
SkBitmap::Allocator* allocator = NULL);
/** Platforms can also optionally overwrite the convolution functions
if we have SIMD versions of them.
static void PlatformConvolutionProcs(SkConvolutionProcs*);