This is the format for resources of type GFXRES (these have the extension
.ani in the original source).

Everything is stored MSB first unless otherwise specified.

position   length  meaning
           4       0xffffffff if the file is uncompressed.
                   Otherwise, the file is compressed. When uncompressed, the
                   file complies with the rest of the format as described
                   below.
           4       Unused in file, always 0x00000000
           4       FlagsAndIndex:
                     bits 0-11: 1 less than the number of frames in this
                                graphics resource
                     bits 12-15: flags:
                       - bit 0: (WANT_MASK)
                       - bit 1: (WANT_PIXMAP)
                       - bit 2: (WANT_COMPRESSED)
                       - bit 3: (DOUBLE_RES)
                     bits 16-31: unknown (0x0000)

Frame descriptions:
Then for all frames:
           4       Type index and flags (TypeIndexAndFlags)
                   Low 2 bytes:
                     bits 0-11 is the index of this frame
                     bits 12-15 are the type flags:
                        - bit 12-13:
                          - 0: (ROM_DRAWABLE)
                          - 1: Direct drawable (RAM_DRAWABLE)
                          - 2: (SCREEN_DRAWABLE)
                          - 3: (OVERLAY_DRAWABLE)
                   High 2 bytes (frame flags):
                      - bits 0-7: global PLUT to use
                      - bit 12: Frame is in cel format (DATA_HARDWARE)
                      - bit 13: (DATA_COPY aka DATA_SCREEN)
                      - bit 14: (DATA_PACKED)
                      - bit 15: (X_FLIP)
           4       Hot spot information (definition of (0, 0) in the image):
                      - low 2 bytes: x location of hot spot
                      - high 2 bytes: y location of hot spot
           4       Image bounds:
                      - low 2 bytes: Image width
                      - low 2 bytes: Image height
           4       Offset from beginning of the frame description for this
                   frame to the beginning of the frame.

Frames:
Then for all frames:
  If DATA_HARDWARE is set in the flags for this frame:
           4       Size of image data
           ?       .cel image data
  If DATA_PACKED is set in the flags for this frame: (from 3do/imageint.c)
     for every line in the image (bounds.height lines):
           2       number of bytes used to encode this line
                   The actual number of bytes is computed like so:
                   (number-of-bytes + 2) * 4
           a number of packets of this format:
           


Initial version 2002-10-22, by Serge van den Boom