ico-utils/dist/decodeIco.js

A javascript library to create ICO file from PNG images and extract PNG images from ICO file.

import { isPngSignatureValid, parsePng } from './png-utils.js';
import { getBlob, getArrayBuffer } from './helpers/binaryConverter.js';
import { joinBytesToNumber } from './helpers/bytesConverter.js';
const FILE_HEADER_SIZE = 6;
const IMAGE_HEADER_SIZE = 16;
export async function decodeIco(icoImage) {
    const buffer = await getArrayBuffer(icoImage);
    const uint8 = new Uint8Array(buffer);
    if (isPngSignatureValid(uint8.slice(0, 8))) {
        return [getParsedPngAndBlob(uint8)];
    }
    if (!isIcoSignatureValid(uint8.slice(0, 4))) {
        throw new Error('INVALID_ICO_IMAGE');
    }
    const imagesCount = joinBytesToNumber(Array.from(uint8.slice(4, 6)));
    const initialImagePosition = FILE_HEADER_SIZE + IMAGE_HEADER_SIZE * imagesCount;
    const imagesHeader = Array.from(uint8.slice(FILE_HEADER_SIZE, initialImagePosition));
    const imagesDetails = getImagesDetails(imagesHeader);
    const images = imagesDetails.map((imageDetails) => {
        const imageUint8 = uint8.slice(imageDetails.position, imageDetails.position + imageDetails.size);
        return getParsedPngAndBlob(imageUint8);
    });
    return images;
}
function getImagesDetails(imagesHeader) {
    if (imagesHeader.length < 1) {
        return [];
    }
    const imageHeader = imagesHeader.splice(0, IMAGE_HEADER_SIZE);
    const position = joinBytesToNumber(imageHeader.slice(12, 16));
    const size = joinBytesToNumber(imageHeader.slice(8, 12));
    return [{ position, size }, ...getImagesDetails(imagesHeader)];
}
function isIcoSignatureValid(imageSignatureBytes) {
    const icoSignatureBytes = [0x00, 0x00, 0x01, 0x00];
    return icoSignatureBytes.toString() === imageSignatureBytes.toString();
}
function getParsedPngAndBlob(uint8) {
    return Object.assign(Object.assign({}, parsePng(uint8)), { blob: getBlob(uint8) });
}