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      1 /*
      2  * Copyright 2013 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef SkBitmapScaler_DEFINED
      9 #define SkBitmapScaler_DEFINED
     10 
     11 #include "SkBitmap.h"
     12 #include "SkConvolver.h"
     13 
     14 /** \class SkBitmapScaler
     15 
     16     Provides the interface for high quality image resampling.
     17  */
     18 
     19 class SK_API SkBitmapScaler {
     20 public:
     21     enum ResizeMethod {
     22         // Quality Methods
     23         //
     24         // Those enumeration values express a desired quality/speed tradeoff.
     25         // They are translated into an algorithm-specific method that depends
     26         // on the capabilities (CPU, GPU) of the underlying platform.
     27         // It is possible for all three methods to be mapped to the same
     28         // algorithm on a given platform.
     29 
     30         // Good quality resizing. Fastest resizing with acceptable visual quality.
     31         // This is typically intended for use during interactive layouts
     32         // where slower platforms may want to trade image quality for large
     33         // increase in resizing performance.
     34         //
     35         // For example the resizing implementation may devolve to linear
     36         // filtering if this enables GPU acceleration to be used.
     37         //
     38         // Note that the underlying resizing method may be determined
     39         // on the fly based on the parameters for a given resize call.
     40         // For example an implementation using a GPU-based linear filter
     41         // in the common case may still use a higher-quality software-based
     42         // filter in cases where using the GPU would actually be slower - due
     43         // to too much latency - or impossible - due to image format or size
     44         // constraints.
     45         RESIZE_GOOD,
     46 
     47         // Medium quality resizing. Close to high quality resizing (better
     48         // than linear interpolation) with potentially some quality being
     49         // traded-off for additional speed compared to RESIZE_BEST.
     50         //
     51         // This is intended, for example, for generation of large thumbnails
     52         // (hundreds of pixels in each dimension) from large sources, where
     53         // a linear filter would produce too many artifacts but where
     54         // a RESIZE_HIGH might be too costly time-wise.
     55         RESIZE_BETTER,
     56 
     57         // High quality resizing. The algorithm is picked to favor image quality.
     58         RESIZE_BEST,
     59 
     60         //
     61         // Algorithm-specific enumerations
     62         //
     63 
     64         // Box filter. This is a weighted average of all of the pixels touching
     65         // the destination pixel. For enlargement, this is nearest neighbor.
     66         //
     67         // You probably don't want this, it is here for testing since it is easy to
     68         // compute. Use RESIZE_LANCZOS3 instead.
     69         RESIZE_BOX,
     70         RESIZE_TRIANGLE,
     71         RESIZE_LANCZOS3,
     72         RESIZE_HAMMING,
     73         RESIZE_MITCHELL,
     74 
     75         // enum aliases for first and last methods by algorithm or by quality.
     76         RESIZE_FIRST_QUALITY_METHOD = RESIZE_GOOD,
     77         RESIZE_LAST_QUALITY_METHOD = RESIZE_BEST,
     78         RESIZE_FIRST_ALGORITHM_METHOD = RESIZE_BOX,
     79         RESIZE_LAST_ALGORITHM_METHOD = RESIZE_MITCHELL,
     80     };
     81 
     82     static bool Resize(SkBitmap* result,
     83                        const SkBitmap& source,
     84                        ResizeMethod method,
     85                        float dest_width, float dest_height,
     86                        SkBitmap::Allocator* allocator = NULL);
     87 
     88     static SkBitmap Resize(const SkBitmap& source,
     89                            ResizeMethod method,
     90                            float dest_width, float dest_height,
     91                            SkBitmap::Allocator* allocator = NULL);
     92 
     93      /** Platforms can also optionally overwrite the convolution functions
     94         if we have SIMD versions of them.
     95       */
     96 
     97     static void PlatformConvolutionProcs(SkConvolutionProcs*);
     98 };
     99 
    100 #endif
    101