Realms of Chaos Masked Tileset Format

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Realms of Chaos Masked Tileset Format
There is no image of a tileset in this format — upload one!
Format typeTileset
HardwareVGA
Max tile count128
PaletteExternal
Tile names?No
Minimum tile size (pixels)16×16
Maximum tile size (pixels)16×16
Plane count1
Plane arrangementLinear
Transparent pixels?Yes
Hitmap pixels?No
Metadata?None
Supports sub-tilesets?No
Compressed tiles?No
Hidden data?No
Games

The MBG Format is used in Realms of Chaos to store "masked" (partially transparent) tile graphics.

File format

Files in this Format contain the following header:

Data type Name Description
UINT16LE[129] offsets Offsets to the start of the pixel data for each tile

Each file can store the tile graphics for up to 128 tiles. The offsets are relative to the start of the pixel data; the pixel data starts at 258 (0x102). The last offset is an offset to the end of the pixel data. offsets[128]+258 should match the size of the file.

The pixel data contains of multiple records in the following format:

Data type Name Description
UINT8 type Type flag for this block
UINT8 count Number of pixel rows covered by this block
BYTE[count*2] pixels 8bpp pixel values (only present if type is 1, 2 or 3)

The order in which the pixels are read from the file is shown here as hexadecimal numbers: 

00 20 40 60 01 21 41 61 80 A0 C0 E0 81 A1 C1 E1
02 22 42 62 03 23 43 63 82 A2 C2 E2 83 A3 C3 E3
04 24 44 64 05 25 45 65 84 A4 C4 E4 85 A5 C5 E5
06 26 46 66 07 27 47 67 86 A6 C6 E6 87 A7 C7 E7
08 28 48 68 09 29 49 69 88 A8 C8 E8 89 A9 C9 E9
0A 2A 4A 6A 0B 2B 4B 6B 8A AA CA EA 8B AB CB EB
0C 2C 4C 6C 0D 2D 4D 6D 8C AC CC EC 8D AD CD ED
0E 2E 4E 6E 0F 2F 4F 6F 8E AE CE EE 8F AF CF EF
10 30 50 70 11 31 51 71 90 B0 D0 F0 91 B1 D1 F1
12 32 52 72 13 33 53 73 92 B2 D2 F2 93 B3 D3 F3
14 34 54 74 15 35 55 75 94 B4 D4 F4 95 B5 D5 F5
16 36 56 76 17 37 57 77 96 B6 D6 F6 97 B7 D7 F7
18 38 58 78 19 39 59 79 98 B8 D8 F8 99 B9 D9 F9
1A 3A 5A 7A 1B 3B 5B 7B 9A BA DA FA 9B BB DB FB
1C 3C 5C 7C 1D 3D 5D 7D 9C BC DC FC 9D BD DD FD
1E 3E 5E 7E 1F 3F 5F 7F 9E BE DE FE 9F BF DF FF

This format appears to be optimized for drawing the masked tiles without needing to check whether or not a pixel is actually transparent. The algorithm to draw the tiles works like this: 

0.  set x and y to the screen-location of the tile image to be drawn
1.  read type and count
2.  IF type = 0
       increase y by count
       go back to 1.
    IF type = 1
       FOR i=1 TO count
          read 2 bytes from file
          write first byte to (x, y)
          write second byte to (x+4, y)
          increase y by 1
       go back to 1.
    IF type = 2
       FOR i=1 TO count
          read 2 bytes from file
          write first byte to (x, y)
          ignore second byte (pixel is transparent)
          increase y by 1
       go back to 1.
    IF type = 3
       FOR i=1 TO count
          read 2 bytes from file
          ignore first byte (pixel is transparent)
          write second byte to (x+4, y)
          increase y by 1
       go back to 1.
    IF type = 4
       set y back to initial screen-location
       increase x by 1
       IF x = 4
          set x to 8
       go back to 1.
    IF type = 5
       * exit

Notes

Each tile seems to end with the following sequence of (type, count) pairs: (4, 0), (0, 0), (5, 0)

The first tile in a file should always be fully transparent, i.e. a sequence of (0, 16), (4, 0) pairs.

When the tileset is to be shown to the user, it should be displayed with a width of 20 tiles (320 pixels).

Credits

This file format was reverse engineered by K1n9_Duk3. If you find this information helpful in a project you're working on, please give credit where credit is due. (A link back to this wiki would be nice too!)

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