CLI script for de-duplicating images references in a glTF asset.

gltf-deduplicate-textures.js

const Listr = require('listr');
const program = require('commander');
const path = require('path');
const fs = require('fs');

const tasks = new Listr([
  {
    title: 'reading file',
    task: (ctx) => {
      if (!ctx.program.output) {
        ctx.program.help();
        throw new Error('Missing required output filepath.');
      }
      ctx.inputPath = path.normalize(ctx.program.args[0]);
      ctx.outputPath = path.normalize(ctx.program.output);
      ctx.gltf = JSON.parse(fs.readFileSync(ctx.inputPath, 'utf8'));
    }
  },
  {
    title: 'de-duplicating images',
    task: (ctx) => {
      const imageMap = ctx.imageMap = {};
      const images = [];
      ctx.gltf.images.forEach((imageDef, imageIndex) => {
        if (!imageDef.uri) {
          throw new Error('GLB assets must be unpacked before use with this tool.');
        } else if (imageMap[imageDef.uri] === undefined) {
          images.push(imageDef);
          imageMap[imageDef.uri] = images.length - 1;
          imageMap[imageIndex] = images.length - 1;
        } else {
          imageMap[imageIndex] = imageMap[imageDef.uri];
        }
      });
      ctx.gltf.images = images;
    }
  },
  {
    title: 'de-duplicating textures',
    task: (ctx) => {
      const textureMap = ctx.textureMap = {};
      const textures = [];
      ctx.gltf.textures.forEach((textureDef, textureIndex) => {
        textureDef.source = ctx.imageMap[textureDef.source];
        const textureKey = `${textureDef.source}:${textureDef.sampler}`;
        if (textureMap[textureKey] === undefined) {
          textures.push(textureDef);
          textureMap[textureKey] = textures.length - 1;
          textureMap[textureIndex] = textures.length - 1;
        } else {
          textureMap[textureIndex] = textureMap[textureKey];
        }
      });
      ctx.gltf.textures = textures;
    }
  },
  {
    title: 'updating materials',
    task: (ctx) => {
      ctx.gltf.materials.forEach((materialDef) => {
        dedupTexture(ctx, materialDef, 'emissiveTexture');
        dedupTexture(ctx, materialDef, 'normalTexture');
        dedupTexture(ctx, materialDef, 'occlusionTexture');
        dedupTexture(ctx, materialDef.pbrMetallicRoughness, 'baseColorTexture');
        dedupTexture(ctx, materialDef.pbrMetallicRoughness, 'metallicRoughnessTexture');
        const specGloss = (materialDef.extensions||{}).KHR_materials_pbrSpecularGlossiness;
        if (specGloss) {
          dedupTexture(ctx, specGloss, 'diffuseTexture');
          dedupTexture(ctx, specGloss, 'specularGlossinessTexture');
        }
      });
    }
  },
  {
    title: 'writing output',
    task: (ctx) => {
      const json = ctx.program.pretty
        ? JSON.stringify(ctx.gltf, null, 2)
        : JSON.stringify(ctx.gltf);
      fs.writeFileSync(ctx.outputPath, json);
    }
  }
]);

function dedupTexture(ctx, def, name) {
  if (def[name]) {
    def[name].index = ctx.textureMap[def[name].index];
  }
}

program
  .version('0.1.0')
  .usage('[options] <inputFile> -o <outputFile>')
  .option('-o, --output [path]', 'output filepath')
  .option('-p, --pretty', 'prettyprint JSON')
  .parse(process.argv);

tasks.run({program: program});