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Non-rectangular images in OMF are stored in this format:

For animations 12, 13 and 14, the index field will be treated as if it were 0. If the index is 0, the data missing field will be treated as if it were 0.

A table of loaded sprite data is maintained. Each loaded frame with a non-zero index is stored into the table in entry number (index + frame number). When the sprite loading code is called, if the g_indexOfReusedSprite value is not -1, and the loaded sprite has data missing == 0, width != 0, index != 0, the data in the file apart from the index will be ignored, and the sprite at the corresponding index in the reuse table will be used instead.

If the data missing flag is zero, the sprite data will follow the sprite header, as length BYTEs. In either case, element index of the sprite reuse table is consulted. If that element is present, or if no graphics data were present in the file, the data from the sprite reuse table are used. Otherwise, that slot in the table is filled with the image data just read from the file.

The sprite data is decoded thusly:

• Initalize X and Y to 0
• Read 1 WORD as P
• Modulus P by 4 to get OPCODE
• Integer divide P by 4 to get DATA
• Compare the OPCODE against the following and take that action
  1. Set X to DATA
  2. While DATA is greater than 0
     1. Read 1 BYTE
        1. Store that byte as the pixel at X,Y in the sprite
        2. Increment X
        3. Decrement DATA
     2. Set X to 0
  3. Set Y to DATA
  4. End of sprite data

Alternative:

 Initalize X and Y to 0
 Read 1 WORD as P
 Modulus P by 4 to get OPCODE
 Integer divide P by 4 to get DATA
 Compare the OPCODE against the following and take that action
   Set X to DATA
   While DATA is greater than 0
     Read 1 BYTE
       Store that byte as the pixel at X,Y in the sprite
       Increment X
       Decrement DATA
     Set X to 0
   Set Y to DATA
   End of sprite data