TXTR (Metroid Prime)
Note: The Tropical Freeze TXTR format is completely different, but doesn't have a page yet.
TXTR is, as the name suggests, the Retro Studios texture format. The format remains completely unchanged from Metroid Prime all the way up to Donkey Kong Country Returns.
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To do: Could possibly use some more information on how the formats work and how to decode them, but then again the Custom Mario Kart Wiiki has this covered pretty nicely already. |
Format
TXTR files contain a very short 12-byte header, followed by the image data.
Header
| Offset | Size | Description |
|---|---|---|
| 0x0 | 4 | Image format. Possible values range from 0x0 to 0xA; see below for more details. |
| 0x4 | 2 | Width |
| 0x6 | 2 | Height |
| 0x8 | 4 | Mipmap count |
| 0xC | End of header | |
Palettes
The C4 and C8 image formats contain a palette table after the header, before the image data begins.
| Offset | Size | Description |
|---|---|---|
| 0x0 | 4 | Palette format. Possible values range from 0 to 2. |
| 0x4 | 2 | Always 0x1 in C4, 0x100 in C8 |
| 0x6 | 2 | Always 0x10 in C4, 0x1 in C8 |
| 0x8 | Varies | Palette colors. 16-bit color values; 16 colors in C4, 256 in C8. |
| End of palette table; image data begins immediately after | ||
Image Formats
There are 11 different image formats; these are built directly into GX, so they remain the same across all GameCube and Wii games. Rather than storing pixels in a linear left-to-right order, GX textures encode pixels in large blocks. The size of the block varies depending on the image format.
For example, suppose you have a format that stores 4x4 blocks. Pixels 1-4 of the image will make up the first row of the first block; pixels 5-8 will make up the second row; 9-12 will make up the third row; 13-16 will make up the fourth row, completing the block; and the 17-20 will begin the first row of the second block, appearing directly to the right of the first row of the first block.
| ID | Name | Bits per pixel | Block size | Description |
|---|---|---|---|---|
| 0x0 | I4 | 4 | 8x8 | 4-bit greyscale intensity values. Two pixels per byte. |
| 0x1 | I8 | 8 | 8x4 | 8-bit greyscale intensity values. |
| 0x2 | IA4 | 8 | 8x4 | 4-bit greyscale intensity values with an additional 4-bit alpha channel. |
| 0x3 | IA8 | 16 | 4x4 | 8-bit greyscale intensity values with an additional 8-bit alpha channel. |
| 0x4 | C4 | 4 | 8x8 | 4-bit palette indices. |
| 0x5 | C8 | 8 | 8x4 | 8-bit palette indices. |
| 0x6 | C14x2 | 16 | 4x4 | Another palette format. Not used by any official textures. |
| 0x7 | RGB565 | 16 | 4x4 | 16-bit colors without alpha. |
| 0x8 | RGB5A3 | 16 | 4x4 | 16-bit colors with alpha. |
| 0x9 | RGBA8 | 32 | 4x4 | Uncompressed 32-bit colors with alpha. |
| 0xA | CMPR | 4 | 8x8 | DXT1-compressed textures. |
External links
- Custom Mario Kart Wiiki: More detailed information on each format, and how to decode them.