SCUMM/Technical Reference/Charset resources

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Revision as of 15:07, 26 May 2005 by Fingolfin (talk | contribs) (Added some V5/V6 charset format info from the SCUMM Reference Guide)
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Character sets define the fonts used by SCUMM to draw text, such as dialogue, on the screen.

V2 charset format


V3 charset format


V4 charset format


V5/V6 charset format

Like all other resources in V5 and later, the charset data is stored in a chunk, in this case a 'CHAR' chunk. The header looks as follows:

Size Type Description
8 chunk tag CHAR chunk tag
6 unknown
15 bytes colour map
1 byte number of bits per pixel
3 unknown
1024 256*quad LE character data offsets

Character glyphs may be 1, 2, 4 or 8 bits per pixel, and can be masked.

The colour map contains the colours each pixel of the character glyph is drawn as. Pixel value 0 is used for transparency; the other values are mapped using the color map in the header.

The character data pointers contain the offset, relative to the byte after the end of the colour map (byte 29), of the character data. This can be 0 if that particular character is not encoded in the character set. The character data itself is formatted as follows:

Size Type Description
1 byte width of character
1 byte height of character
1 byte X offset
1 byte Y offset
many bytes... glyph data bitstream

The X and Y offsets are added to the screen coordinates of the top-left corner of the glyph before drawing. This is useful for, say, shadowed text. Needless to say, glyphs don't all have to be the same size, although in all the examples I have they are the same height.

The data bitstream encodes the pixels in the glyph in left-to-right, top-to-bottom order. Multiple pixels are encoded per byte. The pixels are arranged in big-endian format; so, the first pixel in the stream is in the top bits of the first data byte; then the bits below that; and so on. For example, at one bit per pixel:

Bit position:  7      0 7      0 ...
Words of data: 01234567 89ABCDEF

At two bits per pixel:

Bit position:  7      0 7      0 ...
Words of data: 00112233 44556677

And at four bits per pixel:

Bit position:  7      0 7      1 ...
Words of data: 00001111 22223333

NUT (V7 & V8) charset format