1 2 /* 3 * Copyright 2012 Google Inc. 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 #ifndef SkBitmapTransformer_DEFINED 10 #define SkBitmapTransformer_DEFINED 11 12 #include "SkBitmap.h" 13 14 /** 15 * Class that can copy pixel data out of an SkBitmap, transforming it 16 * into the appropriate PixelFormat. 17 * 18 * As noted in https://codereview.appspot.com/6849119/#msg6 and 19 * https://codereview.appspot.com/6900047 , at some point we might want 20 * to make this more general purpose: 21 * - support more PixelFormats 22 * - use existing SkCanvas::Config8888 enum instead of new PixelFormat enum 23 * - add method to copy pixel data for a single row, instead of the whole bitmap 24 * - add methods to copy pixel data INTO an SkBitmap 25 * 26 * That would allow us to replace SkCopyConfig8888ToBitmap() in 27 * src/core/SkConfig8888.h , as well as the transformations used by 28 * src/images/SkImageDecoder_libpng.cpp , with this common code. 29 * 30 * But for now, we want something more narrowly targeted, just 31 * supplying what is needed by SkBitmapChecksummer. 32 */ 33 class SkBitmapTransformer { 34 public: 35 enum PixelFormat { 36 // 32 bits per pixel, ARGB byte order, with the alpha-channel 37 // value premultiplied into the R/G/B channel values. 38 kARGB_8888_Premul_PixelFormat, 39 40 // marks the end of the list 41 kLast_PixelFormat = kARGB_8888_Premul_PixelFormat, 42 }; 43 44 /** 45 * Creates an SkBitmapTransformer instance that can transform between 46 * the given bitmap and a pixel buffer with given pixelFormat. 47 * 48 * Call IsValid() before using, to confirm that this particular 49 * bitmap/pixelFormat combination is supported! 50 */ 51 SkBitmapTransformer(const SkBitmap& bitmap, PixelFormat pixelFormat) : 52 fBitmap(bitmap), fPixelFormat(pixelFormat) {} 53 54 /** 55 * Returns true iff we can convert between fBitmap and fPixelFormat. 56 * If this returns false, the return values of any other methods will 57 * be meaningless! 58 * 59 * @param logReason whether to log the reason why this combination 60 * is unsupported (only applies in debug mode) 61 */ 62 bool isValid(bool logReason=false) const; 63 64 /** 65 * Returns the number of bytes needed to store a single row of the 66 * bitmap's pixels if converted to pixelFormat. 67 */ 68 size_t bytesNeededPerRow() const { 69 // This is hard-coded for the single supported PixelFormat. 70 return fBitmap.width() * 4; 71 } 72 73 /** 74 * Returns the number of bytes needed to store the entire bitmap 75 * if converted to pixelFormat, ASSUMING that it is written 76 * out as a single contiguous blob of pixels (no leftover bytes 77 * at the end of each row). 78 */ 79 size_t bytesNeededTotal() const { 80 return this->bytesNeededPerRow() * fBitmap.height(); 81 } 82 83 /** 84 * Writes the entire bitmap into dstBuffer, using the already-specified 85 * pixelFormat. Returns true if successful. 86 * 87 * dstBufferSize is the maximum allowable bytes to write into dstBuffer; 88 * if that is not large enough to hold the entire bitmap, then this 89 * will fail immediately and return false. 90 * We force the caller to pass this in to avoid buffer overruns in 91 * unanticipated cases. 92 * 93 * All pixels for all rows will be written into dstBuffer as a 94 * single contiguous blob (no skipped pixels at the end of each 95 * row). 96 */ 97 bool copyBitmapToPixelBuffer (void *dstBuffer, size_t dstBufferSize) const; 98 99 private: 100 const SkBitmap& fBitmap; 101 const PixelFormat fPixelFormat; 102 }; 103 104 #endif 105
