geotiff/dist-module/compression/lerc.js

GeoTIFF image decoding in JavaScript

import { inflate } from 'pako';
// @ts-expect-error
import Lerc from 'lerc';
import { ZSTDDecoder } from 'zstddec';
import BaseDecoder from './basedecoder.js';
import { LercParameters, LercAddCompression } from '../globals.js';
/**
 * @typedef {import('./basedecoder.js').BaseDecoderParameters & { LercParameters?: any }} LercDecoderParameters
 */
export const zstd = new ZSTDDecoder();
export default class LercDecoder extends BaseDecoder {
    /**
     * @param {ArrayBufferLike} buffer
     * @returns {ArrayBufferLike}
     */
    decodeBlock(buffer) {
        const params = /** @type {LercDecoderParameters} */ (this.parameters);
        const addCompression = params.LercParameters?.[LercParameters.AddCompression];
        /** @type {ArrayBufferLike} */
        let decoded = buffer;
        switch (addCompression) {
            case LercAddCompression.None:
                break;
            case LercAddCompression.Deflate:
                decoded = inflate(new Uint8Array(decoded)).buffer;
                break;
            case LercAddCompression.Zstandard:
                decoded = zstd.decode(new Uint8Array(decoded)).buffer;
                break;
            default:
                throw new Error(`Unsupported LERC additional compression method identifier: ${addCompression}`);
        }
        const lercResult = Lerc.decode(decoded, { returnPixelInterleavedDims: this.parameters.planarConfiguration === 1 });
        const lercData = lercResult.pixels[0];
        return lercData.buffer;
    }
}
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