SCUMM/Technical Reference/Charset resources

Introduction

Character sets define the fonts used by SCUMM to draw text, such as dialogue, on the screen.

V1/V2 charset format

The V1 and V2 font format is identical to that found in V3 games; the big difference is that in V1 and V2, the font is not stored in the game data files, but rather is hardcoded into the executable.

Therefore, ScummVM has to include fonts for the various versions of the two affected games (Maniac Mansion and Zak McKracken). The fonts differ depending on the localization of the game.

Currently, ScummVM includes fonts for english, french, german, italian and spanish game variants. It is not known whether there were other localizations, but if you encounter any make sure to tell the team about it!

V3 charset format

The header looks as follows:

Size	Type	Description
4		unknown
1	byte	number of characters
1	byte	height of the font
6	bytes	character width table (one byte for every char)

After this header the character data starts. Every character in the charset takes up exactly 8 bytes, representing 8x8 pixels in which the actual character is contained (the actual width and height of the char should be computed from the charset header).

V4 charset format

The header looks as follows:

Size	Type	Description
2		unknown
15	bytes	colour map
1	byte	number of bits per pixel
1	byte	height of the font
2	short (LE)	number of characters
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

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
4	quad LE	size-23
2	short	version ? (always 0x6303 in dott)
15	bytes	colour map
1	byte	number of bits per pixel
1	byte	height of the font
2	short (LE)	number of characters
nchar*4	nchar*quad LE	character data offsets

Observe that this header is identical to the V4 header with a few bytes added to the start of it. The charset format is otherwise identical to the V4 format described above.

NUT (V7 & V8) charset format

In V7 and V8 (Dig, FT, Comi), the fonts where stored in separate files with the extension "nut". We thus call the format used in these games the "NUT format".

Header of NUT file

Size	Type	Description
4	chunk tag	ANIM chunk tag
4	quad LE	size of ANIM chunk (AHDR and number FRME chunks included)
4	chunk tag	AHDR chunk tag
4	quad LE	size of AHDR chunk (datas until FRME chunk)
2	short LE	number of chars

After AHDR chunk there is FRME chunk for per char of number chars:

Size	Type	Description
4	chunk tag	FRME chunk tag
4	quad LE	size of FRME chunk (with whole FOBJ chunk too)
4	chunk tag	FOBJ chunk tag
4	quad LE	size of FOBJ chunk
2	short LE	id of codec (could be 1, 21, 44)
2	short LE	X display position of char
2	short LE	Y display position of char
2	short LE	width of char
2	short LE	height of char
2	short LE	unknown
2	short LE	unknown
unk	byte	font gfx data, size of data is rest of FRME size