@loaders.gl/textures/src/basis-loader.ts

Framework-independent loaders for compressed and super compressed (basis) textures

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

import type {Loader, LoaderOptions, LoaderWithParser} from '@loaders.gl/loader-utils';
import type {TextureFormat, TextureLevel} from '@loaders.gl/schema';
import {VERSION} from './lib/utils/version';
import {parseBasis} from './lib/parsers/parse-basis';
import type {BasisFormat} from './lib/parsers/parse-basis';

type BasisFormatOption = BasisFormat | Uppercase<BasisFormat>;
type BasisTargetFormat =
  | 'auto'
  | BasisFormatOption
  | {
      alpha: BasisFormatOption;
      noAlpha: BasisFormatOption;
    };

/** Options for the BasisLoader */
export type BasisLoaderOptions = LoaderOptions & {
  /** Options for the BasisLoader */
  basis?: {
    /** Supported texture formats - app would typically query a WebGPU device or WebGL context to obtain the list of supported formats.*/
    supportedTextureFormats?: TextureFormat[];
    /** Override the URL to the worker bundle (by default loads from unpkg.com) */
    workerUrl?: string;

    /** What container format is used? */
    containerFormat?: 'auto' | 'ktx2' | 'basis';
    /** Format for texture data. auto selects based on platform caps (but gl context doesn't exist on a worker thread) */
    format?: BasisTargetFormat;
    /** What module to use for transcoding? */
    module?: 'transcoder' | 'encoder';
  };
};

/**
 * Worker loader for Basis super compressed textures
 */
export const BasisWorkerLoader = {
  dataType: null as unknown as TextureLevel[][],
  batchType: null as never,

  name: 'Basis',
  id: 'basis',
  module: 'textures',
  version: VERSION,
  worker: true,
  extensions: ['basis', 'ktx2'],
  mimeTypes: ['application/octet-stream', 'image/ktx2'],
  tests: ['sB'],
  binary: true,
  options: {
    basis: {
      format: 'auto',
      containerFormat: 'auto',
      module: 'transcoder'
    }
  }
} as const satisfies Loader<TextureLevel[][], never, BasisLoaderOptions>;

/**
 * Loader for Basis super compressed textures
 */
export const BasisLoader = {
  ...BasisWorkerLoader,
  parse: parseBasis
} as const satisfies LoaderWithParser<TextureLevel[][], never, LoaderOptions>;