SCUMM/Technical Reference/Charset resources
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:
|8||chunk tag||CHAR chunk tag|
|1||byte||number of bits per pixel|
|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:
|1||byte||width of character|
|1||byte||height of character|
|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