Compress KTX2 with toktx using Node.js

compress-textures.js

import { exec } from 'child_process';
import fs from 'fs';
import path from 'path';

// This script compresses a single PNG or JPG texture to KTX2 using the Khronos toktx tool.
// Uses low quality but highly compressed ETC1S compression by default.
// Feel free to extend it!

// REQUIREMENTS:
// Install toktx 4.3.1 from https://github.com/KhronosGroup/KTX-Software/releases/tag/v4.3.1

// USAGE: 
// node compress-textures.js [options] input.jpg

// OPTIONS: 
// --high - Use high quality "lossless" UASTC compression
// --medium - Use regular "lossless" UASTC compression
// --low - Use lossy ETC1S compression
// --flip - Flip the texture vertically
// --noMipmaps - Do not generate mipmaps
// --linear - Use linear color space, e.g. for normal maps and other non-color textures such as ORM maps

// EXAMPLE USAGE FOR TEXTURES:
// Albedo:          --low (=etc1s)
// Emissive:        --low (=etc1s)
// Normal:          --high --linear
// ORM:             --high --linear OR --medium --linear
// Transmission:    --medium --linear
// Clearcoat:       --medium --linear

// Additional information: https://github.com/KhronosGroup/3D-Formats-Guidelines/blob/main/KTXArtistGuide.md

const args = process.argv.slice(2);

// Find the input file as the last argument
let input = args[args.length - 1];

// Check if input file exists
if (!fs.existsSync(input)) {
    throw new Error('Input file does not exist');
}

// Find compression, use ETC1S by default
let compression = 'etc1s';
for (let i = 0; i < args.length; i++) {
    if (args[i] === '--medium') {
        compression = 'uastc';
    } else if (args[i] === '--high') {
        compression = 'uastcHighQuality';
    }
}

// Check if --flip flag is present
let flip = '';
for (let i = 0; i < args.length; i++) {
    if (args[i] === '--flip') {
        flip = '--lower_left_maps_to_s0t0';
    }
}

// Build mipmaps by default unless --noMipmaps flag is present
let mipmaps = '--genmipmap';
for (let i = 0; i < args.length; i++) {
    if (args[i] === '--noMipmaps') {
        mipmaps = '';
    }
}

// Linear color space, e.g. for normal maps
let linear = '';
for (let i = 0; i < args.length; i++) {
    if (args[i] === '--linear') {
        linear = '--assign_oetf linear --assign_primaries none';
    }
}

// Set compression command
let command = '';
if (compression === 'etc1s') {
    command = '--t2 --encode etc1s --clevel 4 --qlevel 255';
} else if (compression === 'uastc') {
    command = '--t2 --encode uastc --uastc_quality 4 --uastc_rdo_l .5 --uastc_rdo_d 65536 --zcmp 22';
} else if (compression === 'uastcHighQuality') {
    command = '--t2 --encode uastc --uastc_quality 4 --uastc_rdo_l .2 --uastc_rdo_d 65536 --zcmp 22';
}

// Add new target directory
const parent = path.dirname(input);
const targetDirectory = parent + '/ktx2';
if (!fs.existsSync(targetDirectory)) {
    fs.mkdirSync(targetDirectory);
}

// Set output extensions and path to new targetDirectory
const output = targetDirectory + '/' + path.basename(input.replace(/\.[^/.]+$/, '.ktx2'));

exec(`toktx ${command} ${flip} ${mipmaps} ${output} ${input}`, (error, stdout, stderr) => {
    if (error) {
        console.log(`error when building KTX2: ${error.message}`);
        return;
    }
    if (stderr) {
        console.log(`stderr when building KTX2: ${stderr}`);
        return;
    }
    console.log('Successfully built KTX2 texture');
});

should we not use ktx create ?

You can use the same logic with either basisu or ktx create, yes.