Sprite format

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

Sprite Header

Length 1 WORD Length of sprite
Width 1 WORD Width of the sprite, in pixels
Height 1 WORD Height of the sprite, in pixels
Index 1 BYTE Index of the sprite in already-loaded images table
Data missing 1 BYTE See below

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.

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.

Sprite Data

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
    • 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
  2. Set Y to DATA
  3. End of sprite data