image-size/dist/esm/types/jxl-stream.js

get dimensions of any image file

import { BitReader } from '../utils/bit-reader.js';
import { toHexString } from './utils.js';
function calculateImageDimension(reader, isSmallImage) {
    if (isSmallImage) {
        return 8 * (1 + reader.getBits(5));
    }
    const sizeClass = reader.getBits(2);
    const extraBits = [9, 13, 18, 30][sizeClass];
    return 1 + reader.getBits(extraBits);
}
function calculateImageWidth(reader, isSmallImage, widthMode, height) {
    if (isSmallImage && widthMode === 0) {
        return 8 * (1 + reader.getBits(5));
    }
    if (widthMode === 0) {
        return calculateImageDimension(reader, false);
    }
    const aspectRatios = [1, 1.2, 4 / 3, 1.5, 16 / 9, 5 / 4, 2];
    return Math.floor(height * aspectRatios[widthMode - 1]);
}
export const JXLStream = {
    validate: (input) => {
        return toHexString(input, 0, 2) === 'ff0a';
    },
    calculate(input) {
        const reader = new BitReader(input, 'little-endian');
        const isSmallImage = reader.getBits(1) === 1;
        const height = calculateImageDimension(reader, isSmallImage);
        const widthMode = reader.getBits(3);
        const width = calculateImageWidth(reader, isSmallImage, widthMode, height);
        return { width, height };
    },
};