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/*
* Copyright 2012 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkBitmapTransformer_DEFINED
#define SkBitmapTransformer_DEFINED
#include "SkBitmap.h"
/**
* Class that can copy pixel data out of an SkBitmap, transforming it
* into the appropriate PixelFormat.
*
* As noted in https://codereview.appspot.com/6849119/#msg6 and
* https://codereview.appspot.com/6900047 , at some point we might want
* to make this more general purpose:
* - support more PixelFormats
* - use existing SkCanvas::Config8888 enum instead of new PixelFormat enum
* - add method to copy pixel data for a single row, instead of the whole bitmap
* - add methods to copy pixel data INTO an SkBitmap
*
* That would allow us to replace SkCopyConfig8888ToBitmap() in
* src/core/SkConfig8888.h , as well as the transformations used by
* src/images/SkImageDecoder_libpng.cpp , with this common code.
*
* But for now, we want something more narrowly targeted, just
* supplying what is needed by SkBitmapChecksummer.
*/
class SkBitmapTransformer {
public:
enum PixelFormat {
// 32 bits per pixel, ARGB byte order, with the alpha-channel
// value premultiplied into the R/G/B channel values.
kARGB_8888_Premul_PixelFormat,
// marks the end of the list
kLast_PixelFormat = kARGB_8888_Premul_PixelFormat,
};
/**
* Creates an SkBitmapTransformer instance that can transform between
* the given bitmap and a pixel buffer with given pixelFormat.
*
* Call IsValid() before using, to confirm that this particular
* bitmap/pixelFormat combination is supported!
*/
SkBitmapTransformer(const SkBitmap& bitmap, PixelFormat pixelFormat) :
fBitmap(bitmap), fPixelFormat(pixelFormat) {}
/**
* Returns true iff we can convert between fBitmap and fPixelFormat.
* If this returns false, the return values of any other methods will
* be meaningless!
*
* @param logReason whether to log the reason why this combination
* is unsupported (only applies in debug mode)
*/
bool isValid(bool logReason=false) const;
/**
* Returns the number of bytes needed to store a single row of the
* bitmap's pixels if converted to pixelFormat.
*/
size_t bytesNeededPerRow() const {
// This is hard-coded for the single supported PixelFormat.
return fBitmap.width() * 4;
}
/**
* Returns the number of bytes needed to store the entire bitmap
* if converted to pixelFormat, ASSUMING that it is written
* out as a single contiguous blob of pixels (no leftover bytes
* at the end of each row).
*/
size_t bytesNeededTotal() const {
return this->bytesNeededPerRow() * fBitmap.height();
}
/**
* Writes the entire bitmap into dstBuffer, using the already-specified
* pixelFormat. Returns true if successful.
*
* dstBufferSize is the maximum allowable bytes to write into dstBuffer;
* if that is not large enough to hold the entire bitmap, then this
* will fail immediately and return false.
* We force the caller to pass this in to avoid buffer overruns in
* unanticipated cases.
*
* All pixels for all rows will be written into dstBuffer as a
* single contiguous blob (no skipped pixels at the end of each
* row).
*/
bool copyBitmapToPixelBuffer (void *dstBuffer, size_t dstBufferSize) const;
private:
const SkBitmap& fBitmap;
const PixelFormat fPixelFormat;
};
#endif
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