geotiff/dist-module/compression/packbits.js

GeoTIFF image decoding in JavaScript

import BaseDecoder from './basedecoder.js';
export default class PackbitsDecoder extends BaseDecoder {
    /** @param {ArrayBuffer} buffer */
    decodeBlock(buffer) {
        const dataView = new DataView(buffer);
        const out = [];
        for (let i = 0; i < buffer.byteLength; ++i) {
            let header = dataView.getInt8(i);
            if (header < 0) {
                const next = dataView.getUint8(i + 1);
                header = -header;
                for (let j = 0; j <= header; ++j) {
                    out.push(next);
                }
                i += 1;
            }
            else {
                for (let j = 0; j <= header; ++j) {
                    out.push(dataView.getUint8(i + j + 1));
                }
                i += header + 1;
            }
        }
        return new Uint8Array(out).buffer;
    }
}
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