image/decoders/nsBMPDecoder.h

   1 /* vim:set tw=80 expandtab softtabstop=4 ts=4 sw=4: */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6
   7 #ifndef _nsBMPDecoder_h
   8 #define _nsBMPDecoder_h
   9
  10 #include "nsAutoPtr.h"
  11 #include "gfxColor.h"
  12 #include "Decoder.h"
  13 #include "BMPFileHeaders.h"
  14
  15 namespace mozilla {
  16 namespace image {
  17
  18 class RasterImage;
  19
  20 /**
  21  * Decoder for BMP-Files, as used by Windows and OS/2
  22  */
  23 class nsBMPDecoder : public Decoder
  24 {
  25 public:
  26
  27     nsBMPDecoder(RasterImage &aImage);
  28     ~nsBMPDecoder();
  29
  30     // Specifies whether or not the BMP file will contain alpha data
  31     // If set to true and the BMP is 32BPP, the alpha data will be
  32     // retrieved from the 4th byte of image data per pixel
  33     void SetUseAlphaData(bool useAlphaData);
  34     // Obtains the bits per pixel from the internal BIH header
  35     int32_t GetBitsPerPixel() const;
  36     // Obtains the width from the internal BIH header
  37     int32_t GetWidth() const;
  38     // Obtains the abs-value of the height from the internal BIH header
  39     int32_t GetHeight() const;
  40     // Obtains the internal output image buffer
  41     uint32_t* GetImageData();
  42     // Obtains the size of the compressed image resource
  43     int32_t GetCompressedImageSize() const;
  44     // Obtains whether or not a BMP file had alpha data in its 4th byte
  45     // for 32BPP bitmaps.  Only use after the bitmap has been processed.
  46     bool HasAlphaData() const;
  47
  48     virtual void WriteInternal(const char* aBuffer, uint32_t aCount);
  49     virtual void FinishInternal();
  50
  51 private:
  52
  53     /** Calculates the red-, green- and blueshift in mBitFields using
  54      * the bitmasks from mBitFields */
  55     NS_METHOD CalcBitShift();
  56
  57     uint32_t mPos;
  58
  59     BMPFILEHEADER mBFH;
  60     BITMAPV5HEADER mBIH;
  61     char mRawBuf[WIN_V3_INTERNAL_BIH_LENGTH];
  62
  63     uint32_t mLOH; ///< Length of the header
  64
  65     uint32_t mNumColors; ///< The number of used colors, i.e. the number of entries in mColors
  66     colorTable *mColors;
  67
  68     bitFields mBitFields;
  69
  70     uint8_t *mRow;      ///< Holds one raw line of the image
  71     uint32_t mRowBytes; ///< How many bytes of the row were already received
  72     int32_t mCurLine;   ///< Index of the line of the image that's currently being decoded: [height,1]
  73     int32_t mOldLine;   ///< Previous index of the line
  74     int32_t mCurPos;    ///< Index in the current line of the image
  75
  76     ERLEState mState;   ///< Maintains the current state of the RLE decoding
  77     uint32_t mStateData;///< Decoding information that is needed depending on mState
  78
  79     /** Set mBFH from the raw data in mRawBuf, converting from little-endian
  80      * data to native data as necessary */
  81     void ProcessFileHeader();
  82     /** Set mBIH from the raw data in mRawBuf, converting from little-endian
  83      * data to native data as necessary */
  84     void ProcessInfoHeader();
  85
  86     // Stores whether the image data may store alpha data, or if
  87     // the alpha data is unspecified and filled with a padding byte of 0.
  88     // When a 32BPP bitmap is stored in an ICO or CUR file, its 4th byte
  89     // is used for alpha transparency.  When it is stored in a BMP, its
  90     // 4th byte is reserved and is always 0.
  91     // Reference:
  92     // http://en.wikipedia.org/wiki/ICO_(file_format)#cite_note-9
  93     // Bitmaps where the alpha bytes are all 0 should be fully visible.
  94     bool mUseAlphaData;
  95     // Whether the 4th byte alpha data was found to be non zero and hence used.
  96     bool mHaveAlphaData;
  97 };
  98
  99 /** Sets the pixel data in aDecoded to the given values.
 100  * @param aDecoded pointer to pixel to be set, will be incremented to point to the next pixel.
 101  */
 102 static inline void SetPixel(uint32_t*& aDecoded, uint8_t aRed, uint8_t aGreen, uint8_t aBlue, uint8_t aAlpha = 0xFF)
 103 {
 104     *aDecoded++ = gfxPackedPixel(aAlpha, aRed, aGreen, aBlue);
 105 }
 106
 107 static inline void SetPixel(uint32_t*& aDecoded, uint8_t idx, colorTable* aColors)
 108 {
 109     SetPixel(aDecoded, aColors[idx].red, aColors[idx].green, aColors[idx].blue);
 110 }
 111
 112 /** Sets two (or one if aCount = 1) pixels
 113  * @param aDecoded where the data is stored. Will be moved 4 resp 8 bytes
 114  * depending on whether one or two pixels are written.
 115  * @param aData The values for the two pixels
 116  * @param aCount Current count. Is decremented by one or two.
 117  */
 118 inline void Set4BitPixel(uint32_t*& aDecoded, uint8_t aData,
 119                          uint32_t& aCount, colorTable* aColors)
 120 {
 121     uint8_t idx = aData >> 4;
 122     SetPixel(aDecoded, idx, aColors);
 123     if (--aCount > 0) {
 124         idx = aData & 0xF;
 125         SetPixel(aDecoded, idx, aColors);
 126         --aCount;
 127     }
 128 }
 129
 130 } // namespace image
 131 } // namespace mozilla
 132
 133
 134 #endif
 135