OpenKh

This is a project centralizes all the technical knowledge of Kingdom Hearts series in one place, providing documentation, tools, code libraries and the foundation for modding the commercial games.

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Kingdom Hearts Birth By Sleep - Font archive

At the path arc/system/, the two files font.arc (Japanese font) and fonten.arc (European font) can be found. Those files are nothing more than an archive with all the information needed to render a character or a font image.

Font types

The following font types can be found in both font archives:

Character mapping

Internally, the game engine uses UCS as encoding, meaning that all the Shift-JIS text is ingested and converted on-the-fly to 2-bytes for each character. Then it does a look-up to both INF for FontIcon and COD to match and print that specific character by searching it using the Character ID.

Embedded in the executable, a hard-coded switch table is responsible to convert the characters from 0x21 ('!') to 0x7E (~) into a UCS character.

INF

Describes the texture of a font.

Offset Type Description
00 short How many characters the texture contains.
02 short Texture width.
04 short Texture height.
06 byte Character width.
07 byte Character height.

INF - FontIcon variant

For fonticon, the associated INF file is structured in a completely different way.

Offset Type Description
00 short Character ID
02 byte Left
03 byte Top
04 byte Right
05 byte Bottom
06 short Always 0

Left, Top, Right and Bottom are used to locate the icon in the texture

MTX

A 4-bit image (8-bit for fonticon) that stores all the characters in a grid. The texture is swizzled by 256 bytes, which means that the content is stored by 32x16 pixel blocks at the time (16x16 for fonticon since it is in 8-bit).

The texture size will be smaller than width * height * bpp / 8 bytes long since it is swizzled. That means that the image content at the bottom-right does not contain any data since the 32x16 pixel blocks are not needed to be stored.

Since the colors of each pixel is indexed, a color look-up table is provided.

CLU

A 1024 bytes long file that stores one or more palettes for a given MTX.

For 4-bit MTXs, this file will contain up to 4 different palettes of 16 colors, but is most likely that only the first two are actually used.

For font files, switching between palette 1 and palette 2 will reveal two different contents from the same bitmap, a technique used in Kingdom Hearts II font files too.

For 8-bit MTXs, the file will be considered as a single palette of 256 colors.

The palette format is RGBA (bytes are stored as 0xRR 0xGG 0xBB 0xAA).

COD

Provides the necessary info to print a given character.

Offset Type Description
00 short Character ID.
02 short Position X.
04 short Position Y.
06 byte Palette index.
07 byte Actual character width.

The Character ID is not necessarly unique, for some weird reason. It is used to associate a specific font’s texture area to a given Shift-JIS character.