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Starter PNG parser
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‎CHANGELOG.md‎

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All notable changes to this project will be documented in this file.
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## [1.2.1] - 2024-01-??
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### Added
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- image: Added PNG event-based parser.
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### Changed
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- io: Fix ByteStream bug where skip(0) did not return the ByteStream.
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## [1.2.0] - 2024-01-15
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### Added

‎image/parsers/png.js‎

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/*
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* png.js
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*
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* An event-based parser for PNG images.
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*
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* Licensed under the MIT License
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*
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* Copyright(c) 2024 Google Inc.
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*/
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import * as fs from 'node:fs'; // TODO: Remove.
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import { ByteStream } from '../../io/bytestream.js';
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// https://en.wikipedia.org/wiki/PNG#File_format
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// https://www.w3.org/TR/2003/REC-PNG-20031110
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const SIG = new Uint8Array([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);
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/** @enum {string} */
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export const PngParseEventType = {
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IHDR: 'image_header',
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PLTE: 'palette',
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IDAT: 'image_data',
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};
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/** @enum {number} */
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export const PngColorType = {
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GREYSCALE: 0,
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TRUE_COLOR: 2,
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INDEXED_COLOR: 3,
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GREYSCALE_WITH_ALPHA: 4,
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TRUE_COLOR_WITH_ALPHA: 6,
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};
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/** @enum {number} */
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export const PngInterlaceMethod = {
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NO_INTERLACE: 0,
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ADAM7_INTERLACE: 1,
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}
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/**
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* @typedef PngImageHeader
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* @property {number} width
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* @property {number} height
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* @property {number} bitDepth
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* @property {PngColorType} colorType
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* @property {number} compressionMethod
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* @property {number} filterMethod
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* @property {number} interlaceMethod
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*/
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export class PngImageHeaderEvent extends Event {
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/** @param {PngImageHeader} */
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constructor(header) {
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super(PngParseEventType.IHDR);
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/** @type {PngImageHeader} */
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this.imageHeader = header;
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}
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}
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/**
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* @typedef PngColor
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* @property {number} red
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* @property {number} green
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* @property {number} blue
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*/
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/**
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* @typedef PngPalette
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* @property {PngColor[]} entries
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*/
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export class PngPaletteEvent extends Event {
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/** @param {PngPalette} */
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constructor(palette) {
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super(PngParseEventType.PLTE);
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/** @type {PngPalette} */
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this.palette = palette;
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}
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}
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/**
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* @typedef PngImageData
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* @property {Uint8Array} rawImageData
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*/
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export class PngImageDataEvent extends Event {
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/** @param {PngImageData} */
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constructor(data) {
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super(PngParseEventType.IDAT);
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/** @type {PngImageData} */
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this.data = data;
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}
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}
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/**
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* @typedef PngChunk Internal use only.
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* @property {number} length
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* @property {string} chunkType
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* @property {ByteStream} chunkStream Do not read more than length!
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* @property {number} crc
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*/
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export class PngParser extends EventTarget {
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/**
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* @type {ByteStream}
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* @private
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*/
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bstream;
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/**
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* @type {PngColorType}
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* @private
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*/
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colorType;
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/** @param {ArrayBuffer} ab */
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constructor(ab) {
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super();
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this.bstream = new ByteStream(ab);
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this.bstream.setBigEndian();
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}
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/**
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* Type-safe way to bind a listener for a PngImageHeaderEvent.
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* @param {function(PngImageHeaderEvent): void} listener
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* @returns {PngParser} for chaining
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*/
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onImageHeader(listener) {
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super.addEventListener(PngParseEventType.IHDR, listener);
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return this;
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}
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/**
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* Type-safe way to bind a listener for a PngPaletteEvent.
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* @param {function(PngPaletteEvent): void} listener
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* @returns {PngParser} for chaining
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*/
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onPalette(listener) {
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super.addEventListener(PngParseEventType.PLTE, listener);
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return this;
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}
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/**
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* Type-safe way to bind a listener for a PngImageDataEvent.
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* @param {function(PngImageDataEvent): void} listener
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* @returns {PngParser} for chaining
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*/
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onImageData(listener) {
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super.addEventListener(PngParseEventType.IDAT, listener);
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return this;
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}
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/** @returns {Promise<void>} A Promise that resolves when the parsing is complete. */
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async start() {
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const sigLength = SIG.byteLength;
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const sig = this.bstream.readBytes(sigLength);
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for (let sb = 0; sb < sigLength; ++sb) {
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if (sig[sb] !== SIG[sb]) throw `Bad PNG signature: ${sig}`;
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}
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/** @type {PngChunk} */
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let chunk;
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do {
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const length = this.bstream.readNumber(4);
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chunk = {
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length,
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chunkType: this.bstream.readString(4),
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chunkStream: this.bstream.tee(),
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crc: this.bstream.skip(length).readNumber(4),
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};
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const chStream = chunk.chunkStream;
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switch (chunk.chunkType) {
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// https://www.w3.org/TR/2003/REC-PNG-20031110/#11IHDR
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case 'IHDR':
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if (this.colorType) throw `Found multiple IHDR chunks`;
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/** @type {PngImageHeader} */
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const header = {
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width: chStream.readNumber(4),
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height: chStream.readNumber(4),
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bitDepth: chStream.readNumber(1),
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colorType: chStream.readNumber(1),
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compressionMethod: chStream.readNumber(1),
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filterMethod: chStream.readNumber(1),
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interlaceMethod: chStream.readNumber(1),
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};
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if (!Object.values(PngColorType).includes(header.colorType)) {
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throw `Bad PNG color type: ${header.colorType}`;
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}
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if (header.compressionMethod !== 0) {
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throw `Bad PNG compression method: ${header.compressionMethod}`;
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}
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if (header.filterMethod !== 0) {
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throw `Bad PNG filter method: ${header.filterMethod}`;
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}
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if (!Object.values(PngInterlaceMethod).includes(header.interlaceMethod)) {
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throw `Bad PNG interlace method: ${header.interlaceMethod}`;
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}
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this.colorType = header.colorType;
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this.dispatchEvent(new PngImageHeaderEvent(header));
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break;
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// https://www.w3.org/TR/2003/REC-PNG-20031110/#11PLTE
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case 'PLTE':
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if (this.colorType === undefined) throw `PLTE before IHDR`;
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if (this.colorType === PngColorType.GREYSCALE ||
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this.colorType === PngColorType.GREYSCALE_WITH_ALPHA) throw `PLTE with greyscale`;
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if (length % 3 !== 0) throw `PLTE length was not divisible by 3`;
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/** @type {PngColor[]} */
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const paletteEntries = [];
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for (let p = 0; p < length / 3; ++p) {
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paletteEntries.push({
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red: chStream.readNumber(1),
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green: chStream.readNumber(1),
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blue: chStream.readNumber(1),
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});
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}
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const palette = {
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paletteEntries,
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};
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this.dispatchEvent(new PngPaletteEvent(palette));
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break;
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// https://www.w3.org/TR/2003/REC-PNG-20031110/#11IDAT
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case 'IDAT':
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/** @type {PngImageData} */
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const data = {
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rawImageData: chStream.readBytes(chunk.length),
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};
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this.dispatchEvent(new PngImageDataEvent(data));
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break;
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case 'IEND':
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break;
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default:
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console.log(`Found an unhandled chunk: ${chunk.chunkType}`);
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break;
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}
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} while (chunk.chunkType !== 'IEND');
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}
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}
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const FILES = `PngSuite.png basn0g04.png bggn4a16.png cs8n2c08.png f03n2c08.png g10n3p04.png s01i3p01.png s32i3p04.png tbbn0g04.png xd0n2c08.png
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basi0g01.png basn0g08.png bgwn6a08.png cs8n3p08.png f04n0g08.png g25n0g16.png s01n3p01.png s32n3p04.png tbbn2c16.png xd3n2c08.png
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basi0g02.png basn0g16.png bgyn6a16.png ct0n0g04.png f04n2c08.png g25n2c08.png s02i3p01.png s33i3p04.png tbbn3p08.png xd9n2c08.png
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basi0g04.png basn2c08.png ccwn2c08.png ct1n0g04.png f99n0g04.png g25n3p04.png s02n3p01.png s33n3p04.png tbgn2c16.png xdtn0g01.png
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basi0g08.png basn2c16.png ccwn3p08.png cten0g04.png g03n0g16.png oi1n0g16.png s03i3p01.png s34i3p04.png tbgn3p08.png xhdn0g08.png
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basi0g16.png basn3p01.png cdfn2c08.png ctfn0g04.png g03n2c08.png oi1n2c16.png s03n3p01.png s34n3p04.png tbrn2c08.png xlfn0g04.png
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basi2c08.png basn3p02.png cdhn2c08.png ctgn0g04.png g03n3p04.png oi2n0g16.png s04i3p01.png s35i3p04.png tbwn0g16.png xs1n0g01.png
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basi2c16.png basn3p04.png cdsn2c08.png cthn0g04.png g04n0g16.png oi2n2c16.png s04n3p01.png s35n3p04.png tbwn3p08.png xs2n0g01.png
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basi3p01.png basn3p08.png cdun2c08.png ctjn0g04.png g04n2c08.png oi4n0g16.png s05i3p02.png s36i3p04.png tbyn3p08.png xs4n0g01.png
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basi3p02.png basn4a08.png ch1n3p04.png ctzn0g04.png g04n3p04.png oi4n2c16.png s05n3p02.png s36n3p04.png tm3n3p02.png xs7n0g01.png
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basi3p04.png basn4a16.png ch2n3p08.png exif2c08.png g05n0g16.png oi9n0g16.png s06i3p02.png s37i3p04.png tp0n0g08.png z00n2c08.png
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basi3p08.png basn6a08.png cm0n0g04.png f00n0g08.png g05n2c08.png oi9n2c16.png s06n3p02.png s37n3p04.png tp0n2c08.png z03n2c08.png
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basi4a08.png basn6a16.png cm7n0g04.png f00n2c08.png g05n3p04.png pp0n2c16.png s07i3p02.png s38i3p04.png tp0n3p08.png z06n2c08.png
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basi4a16.png bgai4a08.png cm9n0g04.png f01n0g08.png g07n0g16.png pp0n6a08.png s07n3p02.png s38n3p04.png tp1n3p08.png z09n2c08.png
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basi6a08.png bgai4a16.png cs3n2c16.png f01n2c08.png g07n2c08.png ps1n0g08.png s08i3p02.png s39i3p04.png xc1n0g08.png
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basi6a16.png bgan6a08.png cs3n3p08.png f02n0g08.png g07n3p04.png ps1n2c16.png s08n3p02.png s39n3p04.png xc9n2c08.png
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basn0g01.png bgan6a16.png cs5n2c08.png f02n2c08.png g10n0g16.png ps2n0g08.png s09i3p02.png s40i3p04.png xcrn0g04.png
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basn0g02.png bgbn4a08.png cs5n3p08.png f03n0g08.png g10n2c08.png ps2n2c16.png s09n3p02.png s40n3p04.png xcsn0g01.png`
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.replace(/\s+/g, ' ')
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.split(' ')
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.map(fn => `tests/image-testfiles/${fn}`);
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async function main() {
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for (const fileName of FILES) {
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if (!fileName.includes('3p')) continue;
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console.log(`file: ${fileName}`);
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const nodeBuf = fs.readFileSync(fileName);
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const ab = nodeBuf.buffer.slice(nodeBuf.byteOffset, nodeBuf.byteOffset + nodeBuf.length);
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const parser = new PngParser(ab);
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parser.onImageHeader(evt => {
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// console.dir(evt.imageHeader);
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});
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parser.onPalette(evt => {
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console.dir(evt.palette);
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});
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parser.onImageData(evt => {
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// console.dir(evt);
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});
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try {
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await parser.start();
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} catch (err) {
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if (!fileName.startsWith('tests/image-testfiles/x')) throw err;
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}
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}
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}
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main();

‎tests/image-parsers-jpeg.spec.js‎

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import { JpegParser } from '../image/parsers/jpeg.js';
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import { ExifDataFormat, ExifTagNumber } from '../image/parsers/exif.js';
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/**
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* @typedef {import('../image/parsers/jpeg.js').JpegStartOfFrame} JpegStartOfFrame
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*/
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/**
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* @typedef {import('../image/parsers/exif.js').ExifValue} ExifValue
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*/
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/** @typedef {import('../image/parsers/jpeg.js').JpegStartOfFrame} JpegStartOfFrame */
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/** @typedef {import('../image/parsers/exif.js').ExifValue} ExifValue */
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const FILE_LONG_DESC = 'tests/image-testfiles/long_description.jpg'
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‎tests/image-parsers-png.spec.js‎

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import * as fs from 'node:fs';
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import 'mocha';
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import { expect } from 'chai';
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import { PngColorType, PngInterlaceMethod, PngParser } from '../image/parsers/png.js';
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import { fail } from 'node:assert';
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/** @typedef {import('../image/parsers/png.js').PngImageHeader} PngImageHeader */
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/** @typedef {import('../image/parsers/png.js').PngImageData} PngImageData */
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function getPngParser(fileName) {
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const nodeBuf = fs.readFileSync(fileName);
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const ab = nodeBuf.buffer.slice(nodeBuf.byteOffset, nodeBuf.byteOffset + nodeBuf.length);
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return new PngParser(ab);
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}
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describe('bitjs.image.parsers.PngParser', () => {
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describe('IHDR', () => {
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it('extracts IHDR', async () => {
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/** @type {PngImageHeader} */
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let header;
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await getPngParser('tests/image-testfiles/PngSuite.png')
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.onImageHeader(evt => { header = evt.imageHeader })
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.start();
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expect(header.width).equals(256);
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expect(header.height).equals(256);
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expect(header.bitDepth).equals(8);
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expect(header.colorType).equals(PngColorType.TRUE_COLOR);
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expect(header.compressionMethod).equals(0);
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expect(header.filterMethod).equals(0);
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expect(header.interlaceMethod).equals(PngInterlaceMethod.NO_INTERLACE);
33+
});
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it('throws on corrupt signature', async () => {
36+
/** @type {PngImageHeader} */
37+
let header;
38+
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try {
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await getPngParser('tests/image-testfiles/xs1n0g01.png')
41+
.onImageHeader(evt => { header = evt.imageHeader })
42+
.start();
43+
throw new Error(`PngParser did not throw an error for corrupt PNG signature`);
44+
} catch (err) {
45+
expect(err.startsWith('Bad PNG signature')).equals(true);
46+
}
47+
});
48+
});
49+
50+
it('extracts IDAT', async () => {
51+
/** @type {PngImageData} */
52+
let data;
53+
54+
await getPngParser('tests/image-testfiles/PngSuite.png')
55+
.onImageData(evt => { data = evt.data })
56+
.start();
57+
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expect(data.rawImageData.byteLength).equals(2205);
59+
expect(data.rawImageData[0]).equals(120);
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});
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});

‎tests/image-testfiles/PngSuite.png‎

2.21 KB
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‎tests/image-testfiles/xs1n0g01.png‎

164 Bytes
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