The BMP RLE 8 Compression Algorithm

Original Documentation

--- BMP RLE_8 compression

          The BMP can be compressed in two modes, absolute mode and RLE
          mode. Both modes can occur anywhere in a single bitmap.

          The RLE mode is a simple RLE mechanism, the first byte contains the
          count, the second byte the pixel to be replicatet. If the count byte
          is 0, the second byte is a special, like EOL or delta.

          In absolute mode, the second byte contains the number of bytes to be
          copied litteraly. Each absolute run must be word-aligned that means you
          will may have to add an aditional padding byte which is not included
          in the count. After an absolute run, RLE compression continues.

          Second byte           Meaning

                 0              End of line
                 1              End of bitmap
                 2              Delta. The next two bytes are the horizontal
                                and vertical offsets from the current position
                                to the next pixel.
             3-255              Switch to absolute mode

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