gecko-dev/image/decoders/nsBMPDecoder.h

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/* vim:set tw=80 expandtab softtabstop=4 ts=4 sw=4: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef _nsBMPDecoder_h
#define _nsBMPDecoder_h
#include "nsAutoPtr.h"
#include "imgIDecoderObserver.h"
#include "gfxColor.h"
#include "Decoder.h"
#include "BMPFileHeaders.h"
namespace mozilla {
namespace image {
class RasterImage;
/**
* Decoder for BMP-Files, as used by Windows and OS/2
*/
class nsBMPDecoder : public Decoder
{
public:
nsBMPDecoder(RasterImage &aImage, imgIDecoderObserver* aObserver);
~nsBMPDecoder();
// Specifies whether or not the BMP file will contain alpha data
// If set to true and the BMP is 32BPP, the alpha data will be
// retrieved from the 4th byte of image data per pixel
void SetUseAlphaData(bool useAlphaData);
// Obtains the bits per pixel from the internal BIH header
PRInt32 GetBitsPerPixel() const;
// Obtains the width from the internal BIH header
PRInt32 GetWidth() const;
// Obtains the abs-value of the height from the internal BIH header
PRInt32 GetHeight() const;
// Obtains the internal output image buffer
PRUint32* GetImageData();
// Obtains the size of the compressed image resource
PRInt32 GetCompressedImageSize() const;
// Obtains whether or not a BMP file had alpha data in its 4th byte
// for 32BPP bitmaps. Only use after the bitmap has been processed.
bool HasAlphaData() const;
virtual void WriteInternal(const char* aBuffer, PRUint32 aCount);
virtual void FinishInternal();
private:
/** Calculates the red-, green- and blueshift in mBitFields using
* the bitmasks from mBitFields */
NS_METHOD CalcBitShift();
PRUint32 mPos;
BMPFILEHEADER mBFH;
BITMAPV5HEADER mBIH;
char mRawBuf[WIN_V3_INTERNAL_BIH_LENGTH];
PRUint32 mLOH; ///< Length of the header
PRUint32 mNumColors; ///< The number of used colors, i.e. the number of entries in mColors
colorTable *mColors;
bitFields mBitFields;
PRUint32 *mImageData; ///< Pointer to the image data for the frame
PRUint8 *mRow; ///< Holds one raw line of the image
PRUint32 mRowBytes; ///< How many bytes of the row were already received
PRInt32 mCurLine; ///< Index of the line of the image that's currently being decoded: [height,1]
PRInt32 mOldLine; ///< Previous index of the line
PRInt32 mCurPos; ///< Index in the current line of the image
ERLEState mState; ///< Maintains the current state of the RLE decoding
PRUint32 mStateData;///< Decoding information that is needed depending on mState
/** Set mBFH from the raw data in mRawBuf, converting from little-endian
* data to native data as necessary */
void ProcessFileHeader();
/** Set mBIH from the raw data in mRawBuf, converting from little-endian
* data to native data as necessary */
void ProcessInfoHeader();
// Stores whether the image data may store alpha data, or if
// the alpha data is unspecified and filled with a padding byte of 0.
// When a 32BPP bitmap is stored in an ICO or CUR file, its 4th byte
// is used for alpha transparency. When it is stored in a BMP, its
// 4th byte is reserved and is always 0.
// Reference:
// http://en.wikipedia.org/wiki/ICO_(file_format)#cite_note-9
// Bitmaps where the alpha bytes are all 0 should be fully visible.
bool mUseAlphaData;
// Whether the 4th byte alpha data was found to be non zero and hence used.
bool mHaveAlphaData;
};
/** Sets the pixel data in aDecoded to the given values.
* @param aDecoded pointer to pixel to be set, will be incremented to point to the next pixel.
*/
static inline void SetPixel(PRUint32*& aDecoded, PRUint8 aRed, PRUint8 aGreen, PRUint8 aBlue, PRUint8 aAlpha = 0xFF)
{
*aDecoded++ = GFX_PACKED_PIXEL(aAlpha, aRed, aGreen, aBlue);
}
static inline void SetPixel(PRUint32*& aDecoded, PRUint8 idx, colorTable* aColors)
{
SetPixel(aDecoded, aColors[idx].red, aColors[idx].green, aColors[idx].blue);
}
/** Sets two (or one if aCount = 1) pixels
* @param aDecoded where the data is stored. Will be moved 4 resp 8 bytes
* depending on whether one or two pixels are written.
* @param aData The values for the two pixels
* @param aCount Current count. Is decremented by one or two.
*/
inline void Set4BitPixel(PRUint32*& aDecoded, PRUint8 aData,
PRUint32& aCount, colorTable* aColors)
{
PRUint8 idx = aData >> 4;
SetPixel(aDecoded, idx, aColors);
if (--aCount > 0) {
idx = aData & 0xF;
SetPixel(aDecoded, idx, aColors);
--aCount;
}
}
} // namespace image
} // namespace mozilla
#endif