# TEXT chunk (textures)

Source: groove.exe `FUN_004067b0` (size pass), `FUN_004071d0` → `FUN_00406880` (palettes),
`FUN_00406ab0` (pages), `FUN_00406a10` (RLE), `FUN_00406d30` (texture list),
`FUN_00406e40` (texture animations), `FUN_00407240`/`FUN_00408470` (upload/conversion).
Tools: `tools/textchunk.py`, `tools/text_export.py`. Parse + rebuild is **byte-identical
for all level WADs** (the RLE encoder also reproduces the original data exactly).

## Layout
```
u32 nPal                         (0 in all WADs)
  nPal × { u32 id, u32 n, u16 colour[n], u8 extra[n] }
u32 nPages                       (13–22 per level, all 256×256)
  nPages × { u32 flags, u32 w, u32 h, data }
     flags == 0     : w·h bytes (8 bit, palette)                – unused
     flags & 0x80   : u32 length, RLE16                         – all original pages
     otherwise      : w·h u16 raw
u32 nTex                         (~180–1260)
  nTex × 8 bytes { u16 flags, u8 page, u8 clut(0xff), u8 x0, u8 x1, u8 y0, u8 y1 }   (edges inclusive)
u32 nAnim
  nAnim × { u16 texIndex, u8 type, payload per type }
     type 1,2 : 3 bytes        type 7,9 : u16,u16,u8,u8
     type 8   : u8, u8 nFrames, u8, nFrames × u16 texIndex (flipbook)
     type 10,11: u8,u8,u8,u8 n, n × u16 texIndex
```
RLE16: sequence of s16 n; n>0 → n literal u16; n<0 → next u16 repeated (−n) times.

## Pixels
16 bit **PS1 order**: bits 0–4 R, 5–9 G, 10–14 B, bit 15 = STP.
`0x0000` = transparent (the converter writes 0 for pixel 0, everything else is converted).
STP=0 with colour≠0 occurs on pages with a blend mode (semi-transparent pixels).
Export: alpha 0 = 0x0000, alpha 128 = STP 0, alpha 255 = STP 1.

Page flags & 0x7f = format/blend class (table 0x570370, 0x20 bytes each):
1 = opaque, 2 = own converter (0x409640), 3 = opaque+flag, 4/7 = alpha (blend 1),
5 = blend 3, 6 = same as 1. (Modes 1/2/3 ≈ PS1 semi-transparency modes; details open.)

## Texture list
Model faces (TRAK/STPC, face+8 u16) reference an index into the texture list;
entry = rectangle on a page. `flags` low byte 4/5/6/0xc6, high byte 1/4/17/20/36/…
(meaning open; probably blend/size class). For replacing: leave the list unchanged
and only swap pixels in the pages → no cross references affected.

## Export / replace
```
text_export.py export level.wad folder      # pageNN_fXX.png + texinfo.txt (≈370 KB per level)
text_export.py import level.wad folder new.wad
```
Import only changes pixels whose RGBA differs from the export → unchanged pages stay
bit-exact. Size must stay 256×256. Appending new pages/textures is possible
(increase nTex/nPages), but then faces in TRAK/STPC must use the new indices.