@loaders.gl/textures/dist/lib/utils/extract-mipmap-images.js

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

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
import { getTextureFormatFromWebGLFormat, getWebGLFormatFromTextureFormat } from "./texture-format-map.js";
/**
 * Extract mipmap images from compressed texture buffer
 * @param data - binary data of compressed texture or Array of level objects
 * @param options.mipMapLevels - number of mipmap level inside image
 * @param options.width - width of 0 - level
 * @param options.height - height of 0 - level
 * @param options.sizeFunction - format-related function to calculate level size in bytes
 * @param options.internalFormat - WebGL compatible format code
 * @param options.textureFormat - canonical loaders.gl texture format
 * @returns Array of the texture levels
 */
export function extractMipmapImages(data, options) {
    const images = new Array(options.mipMapLevels);
    const textureFormat = options.textureFormat || getTextureFormatFromWebGLFormat(options.internalFormat);
    const format = options.internalFormat || getWebGLFormatFromTextureFormat(options.textureFormat);
    let levelWidth = options.width;
    let levelHeight = options.height;
    let offset = 0;
    for (let i = 0; i < options.mipMapLevels; ++i) {
        // @ts-expect-error
        const levelSize = getLevelSize(options, levelWidth, levelHeight, data, i);
        // @ts-expect-error
        const levelData = getLevelData(data, i, offset, levelSize);
        const image = {
            shape: 'texture-level',
            compressed: true,
            data: levelData,
            width: levelWidth,
            height: levelHeight,
            levelSize
        };
        if (format !== undefined) {
            image.format = format;
        }
        if (textureFormat) {
            image.textureFormat = textureFormat;
        }
        images[i] = image;
        levelWidth = Math.max(1, levelWidth >> 1);
        levelHeight = Math.max(1, levelHeight >> 1);
        offset += levelSize;
    }
    return images;
}
function getLevelData(data, index, offset, levelSize) {
    if (!Array.isArray(data)) {
        return new Uint8Array(data.buffer, data.byteOffset + offset, levelSize);
    }
    return data[index].levelData;
}
function getLevelSize(options, levelWidth, levelHeight, data, index) {
    if (!Array.isArray(data)) {
        return options.sizeFunction(levelWidth, levelHeight);
    }
    return options.sizeFunction(data[index]);
}
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