ac-dds

Writes DDS textures Assetto Corsa reads correctly, decodes them back to RGBA in Node or a browser, and says why the game would mishandle one. AC is a DX9 engine, and a texture it cannot use still installs and loads: the only symptom is a car that looks wrong.

import { caseCollisions, ddsInfo, ddsProblems, decodeDds, encodeDds } from "ac-dds"

const dds = encodeDds(rgba, 2048, 2048, { alpha: true }) // a Buffer: DXT5, 12 mip levels
decodeDds(dds.buffer.slice(dds.byteOffset, dds.byteOffset + dds.length)) // { width, height, pixels }

ddsInfo(bytes)     // { width, height, mips, fourCC, alpha, dx10 }, or null
ddsProblems(bytes) // [{ code: "mip-chain", message: "It has no mipmaps where ..." }]
caseCollisions(["Body.dds", "body.dds", "rim.dds"]) // [["Body.dds", "body.dds"]]

• Encoder: BC1 (DXT1) or, with alpha, BC3 (DXT5), with every mip level down to 1x1 and the classic DX9 header, never DX10. The chain is counted to the longer edge, so 2048x512 gets 12 levels, and each level is averaged weighted by alpha, so a cut-out's clear black never darkens its edges at a distance. Flat colors come back within one step of themselves.
• Decoder: DXT1, DXT3 and DXT5, the same behind a DX10 header, BC7, and uncompressed RGB, RGBA and luminance read through the header's channel masks. Top level only, and null for anything else rather than a guess.
• Checker: ddsProblems reports not-dds, dx10 (ignored by the game, the classic white car), not-power-of-two (a DX9 game may drop the mip chain), mip-chain (too few levels: shimmers at a distance) and truncated (shorter than its declared levels need), each with a one-line message. caseCollisions finds names that are one file on NTFS, where the second to extract wins.

ac-dds/decode is the decoder alone, with no imports at all, so a browser can load it straight from node_modules through an import map. The rest uses Buffer and is Node only.