gecko-dev/image/decoders/nsBMPDecoder.h

156 lines
5.2 KiB
C++

/* 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 mozilla_image_decoders_nsBMPDecoder_h
#define mozilla_image_decoders_nsBMPDecoder_h
#include "BMPFileHeaders.h"
#include "Decoder.h"
#include "gfxColor.h"
#include "nsAutoPtr.h"
namespace mozilla {
namespace image {
class RasterImage;
/// Decoder for BMP-Files, as used by Windows and OS/2
class nsBMPDecoder : public Decoder
{
public:
~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
int32_t GetBitsPerPixel() const;
// Obtains the width from the internal BIH header
int32_t GetWidth() const;
// Obtains the abs-value of the height from the internal BIH header
int32_t GetHeight() const;
// Obtains the internal output image buffer
uint32_t* GetImageData();
// Obtains the size of the compressed image resource
int32_t 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,
uint32_t aCount) override;
virtual void FinishInternal() override;
private:
friend class DecoderFactory;
friend class nsICODecoder;
// Decoders should only be instantiated via DecoderFactory.
// XXX(seth): nsICODecoder is temporarily an exception to this rule.
explicit nsBMPDecoder(RasterImage* aImage);
/// Calculates the red-, green- and blueshift in mBitFields using
/// the bitmasks from mBitFields
NS_METHOD CalcBitShift();
uint32_t mPos; //< Number of bytes read from aBuffer in WriteInternal()
BMPFILEHEADER mBFH;
BITMAPV5HEADER mBIH;
char mRawBuf[BIH_INTERNAL_LENGTH::WIN_V3]; //< If this is changed,
// WriteInternal() MUST be updated
uint32_t mLOH; //< Length of the header
uint32_t mNumColors; //< The number of used colors, i.e. the number of
// entries in mColors
colorTable* mColors;
bitFields mBitFields;
uint8_t* mRow; //< Holds one raw line of the image
uint32_t mRowBytes; //< How many bytes of the row were already received
int32_t mCurLine; //< Index of the line of the image that's currently
// being decoded: [height,1]
int32_t mOldLine; //< Previous index of the line
int32_t mCurPos; //< Index in the current line of the image
ERLEState mState; //< Maintains the current state of the RLE decoding
uint32_t 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();
/// True if we've already processed the BMP header.
bool mProcessedHeader;
// 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(uint32_t*& aDecoded, uint8_t aRed, uint8_t aGreen,
uint8_t aBlue, uint8_t aAlpha = 0xFF)
{
*aDecoded++ = gfxPackedPixel(aAlpha, aRed, aGreen, aBlue);
}
static inline void
SetPixel(uint32_t*& aDecoded, uint8_t 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(uint32_t*& aDecoded, uint8_t aData, uint32_t& aCount,
colorTable* aColors)
{
uint8_t idx = aData >> 4;
SetPixel(aDecoded, idx, aColors);
if (--aCount > 0) {
idx = aData & 0xF;
SetPixel(aDecoded, idx, aColors);
--aCount;
}
}
} // namespace image
} // namespace mozilla
#endif // mozilla_image_decoders_nsBMPDecoder_h