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      1 /*
      2  * Copyright 2015 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 #ifndef SkSampler_DEFINED
      8 #define SkSampler_DEFINED
      9 
     10 #include "SkCodec.h"
     11 #include "SkCodecPriv.h"
     12 #include "SkTypes.h"
     13 
     14 class SkSampler : public SkNoncopyable {
     15 public:
     16     /**
     17      *  Update the sampler to sample every sampleX'th pixel. Returns the
     18      *  width after sampling.
     19      */
     20     int setSampleX(int sampleX) {
     21         return this->onSetSampleX(sampleX);
     22     }
     23 
     24     /**
     25      *  Update the sampler to sample every sampleY'th row.
     26      */
     27     void setSampleY(int sampleY) {
     28         fSampleY = sampleY;
     29     }
     30 
     31     /**
     32      *  Retrieve the value set for sampleY.
     33      */
     34     int sampleY() const {
     35         return fSampleY;
     36     }
     37 
     38     /**
     39      *  Based on fSampleY, return whether this row belongs in the output.
     40      *
     41      *  @param row Row of the image, starting with the first row in the subset.
     42      */
     43     bool rowNeeded(int row) const {
     44         return (row - get_start_coord(fSampleY)) % fSampleY == 0;
     45     }
     46 
     47     /**
     48      * Fill the remainder of the destination with a single color
     49      *
     50      * @param info
     51      * Contains the color type of the rows to fill.
     52      * Contains the width of the destination rows to fill
     53      * Contains the number of rows that we need to fill.
     54      *
     55      * @param dst
     56      * The destination row to fill from.
     57      *
     58      * @param rowBytes
     59      * Stride in bytes of the destination.
     60      *
     61      * @param colorOrIndex
     62      * If colorType is kF16, colorOrIndex is treated as a 64-bit color.
     63      * If colorType is kN32, colorOrIndex is treated as a 32-bit color.
     64      * If colorType is k565, colorOrIndex is treated as a 16-bit color.
     65      * If colorType is kGray, colorOrIndex is treated as an 8-bit color.
     66      * If colorType is kIndex, colorOrIndex is treated as an 8-bit index.
     67      * Other SkColorTypes are not supported.
     68      *
     69      * @param zeroInit
     70      * Indicates whether memory is already zero initialized.
     71      *
     72      */
     73     static void Fill(const SkImageInfo& info, void* dst, size_t rowBytes,
     74             uint64_t colorOrIndex, SkCodec::ZeroInitialized zeroInit);
     75 
     76     /**
     77      * Allow subclasses to implement unique versions of fill().
     78      */
     79     virtual void fill(const SkImageInfo& info, void* dst, size_t rowBytes,
     80             uint64_t colorOrIndex, SkCodec::ZeroInitialized zeroInit) {}
     81 
     82     SkSampler()
     83         : fSampleY(1)
     84     {}
     85 
     86     virtual ~SkSampler() {}
     87 private:
     88     int fSampleY;
     89 
     90     virtual int onSetSampleX(int) = 0;
     91 };
     92 
     93 #endif // SkSampler_DEFINED
     94