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Michael Smith
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src/pbm.js
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240
src/pbm.js
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/*
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MIT License
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Copyright (c) 2023 Michael Smith <root@retrospace.be>
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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import BinaryStream from "./binarystream.js";
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class PBM {
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constructor(arrayBuffer) {
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this.binaryStream = new BinaryStream(arrayBuffer);
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// Image properties taken from BMHD chunk
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this.width = null;
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this.height = null;
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this.size = null;
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this.xOrigin = null;
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this.yOrigin = null;
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this.numPlanes = null;
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this.mask = null;
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this.compression = null;
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this.transClr = null;
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this.xAspect = null;
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this.yAspect = null;
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this.pageWidth = null;
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this.pageHeight = null;
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// Palette information taken from CMAP chunk
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this.palette = [];
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// Color cycling information taken from CRNG chunk
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this.cyclingRanges = [];
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// Thumbnail information taken from TINY chunk
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this.thumbnail = {
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width: null,
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height: null,
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size: null,
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palette: this.palette,
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pixelData: [],
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};
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// Uncompressed pixel data referencing palette colors
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this.pixelData = [];
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try {
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this.parseFORM();
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} catch (error) {
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if (error instanceof RangeError) {
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throw new Error(`Failed to parse file.`);
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} else {
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throw error; // re-throw the error unchanged
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}
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}
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}
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parseFORM() {
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// Parse "FORM" chunk
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let chunkID = this.binaryStream.readString(4);
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const lenChunk = this.binaryStream.readUint32BE();
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const formatID = this.binaryStream.readString(4);
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// Validate chunk according to notes on https://en.wikipedia.org/wiki/ILBM
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if (chunkID !== "FORM") {
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throw new Error(
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`Invalid chunkID: "${chunkID}" at byte ${this.binaryStream.index}. Expected "FORM".`
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);
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}
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if (lenChunk !== this.binaryStream.length - 8) {
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throw new Error(
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`Invalid chunk length: ${lenChunk} bytes. Expected ${
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this.binaryStream.length - 8
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} bytes.`
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);
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}
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if (formatID !== "PBM ") {
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throw new Error(`Invalid formatID: "${formatID}". Expected "PBM ".`);
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}
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// Parse all other chunks
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while (!this.binaryStream.EOF()) {
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chunkID = this.binaryStream.readString(4);
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this.binaryStream.jump(4); // Skip 4 bytes chunk length value
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switch (chunkID) {
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case "BMHD":
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this.parseBMHD();
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break;
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case "CMAP":
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this.parseCMAP();
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break;
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case "DPPS":
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// NOTE(m): Ignore unknown DPPS chunk of size 110 bytes
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this.binaryStream.jump(110);
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break;
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case "CRNG":
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this.parseCRNG();
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break;
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case "TINY":
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this.parseTINY();
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break;
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case "BODY":
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this.parseBODY();
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break;
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default:
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throw new Error(
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`Unsupported chunkID: ${chunkID} at byte ${this.binaryStream.index}`
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);
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}
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}
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}
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// Parse Bitmap Header chunk
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parseBMHD() {
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this.width = this.binaryStream.readUint16BE();
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this.height = this.binaryStream.readUint16BE();
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this.size = this.width * this.height;
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this.xOrigin = this.binaryStream.readInt16BE();
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this.yOrigin = this.binaryStream.readInt16BE();
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this.numPlanes = this.binaryStream.readUint8();
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this.mask = this.binaryStream.readUint8();
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this.compression = this.binaryStream.readUint8();
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this.binaryStream.readUint8(); // Ignore pad1 field left "for future compatibility"
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this.transClr = this.binaryStream.readUint16BE();
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this.xAspect = this.binaryStream.readUint8();
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this.yAspect = this.binaryStream.readUint8();
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this.pageWidth = this.binaryStream.readInt16BE();
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this.pageHeight = this.binaryStream.readInt16BE();
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}
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// Parse Palette chunk
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parseCMAP() {
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const numColors = 2 ** this.numPlanes;
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// FIXME(m): Read 3 bytes at a time?
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for (let i = 0; i < numColors; i++) {
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let rgb = [];
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for (let j = 0; j < 3; j++) {
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rgb.push(this.binaryStream.readByte());
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}
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this.palette.push(rgb);
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}
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}
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// Parse Color range chunk
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parseCRNG() {
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this.binaryStream.jump(2); // 2 bytes padding according to https://en.wikipedia.org/wiki/ILBM#CRNG:_Colour_range
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const cyclingRange = {
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rate: this.binaryStream.readInt16BE(),
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flags: this.binaryStream.readInt16BE(),
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low: this.binaryStream.readUint8(),
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hight: this.binaryStream.readUint8(),
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};
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this.cyclingRanges.push(cyclingRange);
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}
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// Parse Thumbnail chunk
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parseTINY() {
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this.thumbnail.width = this.binaryStream.readUint16BE();
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this.thumbnail.height = this.binaryStream.readUint16BE();
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this.thumbnail.size = this.thumbnail.width * this.thumbnail.height;
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while (this.thumbnail.pixelData.length < this.thumbnail.size) {
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const byte = this.binaryStream.readByte();
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// TODO(m): Deduplicate decompression code for thumbnail and image data
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if (this.compression === 1) {
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// Decompress the data
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if (byte > 128) {
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const nextByte = this.binaryStream.readByte();
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for (let i = 0; i < 257 - byte; i++) {
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this.thumbnail.pixelData.push(nextByte);
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}
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} else if (byte < 128) {
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for (let i = 0; i < byte + 1; i++) {
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this.thumbnail.pixelData.push(this.binaryStream.readByte());
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}
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} else {
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break;
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}
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} else {
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// Data is not compressed, just copy the bytes
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this.thumbnail.pixelData.push(byte);
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}
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}
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}
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// Parse Image data chunk
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parseBODY() {
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// NOTE(m): Should we make use of the chunk length here instead?
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while (this.pixelData.length < this.size) {
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const byte = this.binaryStream.readByte();
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if (this.compression === 1) {
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// Decompress the data
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if (byte > 128) {
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const nextByte = this.binaryStream.readByte();
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for (let i = 0; i < 257 - byte; i++) {
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this.pixelData.push(nextByte);
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}
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} else if (byte < 128) {
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for (let i = 0; i < byte + 1; i++) {
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this.pixelData.push(this.binaryStream.readByte());
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}
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} else {
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break;
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}
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} else {
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// Data is not compressed, just copy the bytes
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this.pixelData.push(byte);
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}
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}
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}
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}
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export default PBM;
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