mirror of
https://github.com/danbulant/pngjs
synced 2026-05-27 13:51:50 +00:00
368 lines
9.5 KiB
JavaScript
368 lines
9.5 KiB
JavaScript
// Copyright (c) 2012 Kuba Niegowski
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//
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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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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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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
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// THE SOFTWARE.
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'use strict';
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var util = require('util'),
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Stream = require('stream'),
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Compress = require('./compress'),
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Filter = require('./filter');
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var signature = [0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a];
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var TYPE_IHDR = 0x49484452;
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var TYPE_IEND = 0x49454e44;
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var TYPE_IDAT = 0x49444154;
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var TYPE_PLTE = 0x504c5445;
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var TYPE_tRNS = 0x74524e53;
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var TYPE_gAMA = 0x67414d41;
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var COLOR_PALETTE = 1;
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var COLOR_COLOR = 2;
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var COLOR_ALPHA = 4;
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var Parser = module.exports = function(options) {
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Stream.call(this);
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this._options = options;
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options.checkCRC = options.checkCRC !== false;
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this._hasIHDR = false;
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this._hasIEND = false;
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// input flags
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this._palette = [];
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this._colorType = 0;
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this._chunks = {};
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this._chunks[TYPE_IHDR] = this._parseIHDR.bind(this);
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this._chunks[TYPE_IEND] = this._parseIEND.bind(this);
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this._chunks[TYPE_IDAT] = this._parseIDAT.bind(this);
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this._chunks[TYPE_PLTE] = this._parsePLTE.bind(this);
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this._chunks[TYPE_tRNS] = this._parseTRNS.bind(this);
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this._chunks[TYPE_gAMA] = this._parseGAMA.bind(this);
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this._compress = new Compress(options);
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this._filter = new Filter(options);
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this._initCompress();
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};
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util.inherits(Parser, Stream);
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Parser.prototype._initCompress = function() {
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this._compress.on('error', this.emit.bind(this, 'error'));
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this._compress.on('deflated', this._packData.bind(this));
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this._compress.on('inflated', this._unfilter.bind(this));
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};
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Parser.prototype._parse = function(data) {
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var idx = 0;
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try {
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// check PNG file signature
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while (idx < signature.length) {
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if (data[idx] != signature[idx]) {
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throw new Error('Invalid file signature');
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}
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idx++;
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}
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//console.log('Signature is ok');
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// iterate chunks
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while (idx < data.length) {
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idx = this._parseChunk(data, idx);
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}
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}
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catch(err) {
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this.emit('error', err);
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}
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};
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Parser.prototype._pack = function(width, height, data) {
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// Signature
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this.emit('data', new Buffer(signature));
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this.emit('data', this._packIHDR(width, height));
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// filter pixel data
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var data = this._filter.filter(data, width, height);
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// compress it
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this._compress.deflate(data);
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};
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Parser.prototype._packData = function(data) {
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// console.log('deflate', data.length);
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this.emit('data', this._packIDAT(data));
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this.emit('data', this._packIEND());
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this.emit('end');
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};
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Parser.prototype._unfilter = function(data) {
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// expand data to 32 bit depending on colorType
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if (this._colorType == 0) { // L
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data = this._filter.unfilter(data, 1); // 1 Bpp
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} else if (this._colorType == 2) { // RGB
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data = this._filter.unfilter(data, 3); // 3 Bpp
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} else if (this._colorType == 3) { // I
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data = this._filter.unfilter(data, 1); // 1 Bpp
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// use values fom palette
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var pxLineLength = this.width << 2;
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for (var y = 0; y < this.height; y++) {
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var pxRowPos = y * pxLineLength;
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for (var x = 0; x < this.width; x++) {
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var pxPos = pxRowPos + (x << 2),
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color = this._palette[data[pxPos]];
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for (var i = 0; i < 4; i++)
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data[pxPos + i] = color[i];
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}
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}
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} else if (this._colorType == 4) { // LA
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data = this._filter.unfilter(data, 2); // 2 Bpp
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} else if (this._colorType == 6) { // RGBA
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data = this._filter.unfilter(data, 4); // 4 Bpp
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} else throw new Error('Unsupported color type');
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this.emit('parsed', data);
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};
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Parser.prototype._parseChunk = function(data, idx) {
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if (this._hasIEND)
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throw new Error('Not expected chunk after IEND');
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// chunk size (only content)
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var length = data.readUInt32BE(idx);
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idx += 4;
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// chunk type
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var type = data.readUInt32BE(idx),
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ancillary = !!(data[idx] & 0x20), // or critical
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priv = !!(data[idx+1] & 0x20), // or public
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safeToCopy = !!(data[idx+3] & 0x20), // or unsafe
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name = '';
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for (var i = 0; i < 4; i++)
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name += String.fromCharCode(data[idx+i]);
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idx += 4;
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// console.log('chunk ', name, length);
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// calc CRC (of chunk type and content)
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var calcCrc = crc32(data.slice(idx - 4, idx + length)),
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content = data.slice(idx, idx + length);
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idx += length;
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// read CRC
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var fileCrc = data.readInt32BE(idx);
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idx += 4;
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// and check CRC
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if (this._options.checkCRC && calcCrc != fileCrc)
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throw new Error('Crc error');
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if (!this._hasIHDR && type != TYPE_IHDR)
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throw new Error('Expected IHDR on beggining');
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if (this._chunks[type]) {
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this._chunks[type](content);
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} else if (!ancillary)
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throw new Error('Unsupported critical chunk type ' + name);
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// else
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// console.log('Ignoring chunk', name, type.toString(16));
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return idx;
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};
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Parser.prototype._packChunk = function(type, data) {
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var len = (data ? data.length : 0),
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buf = new Buffer(len + 12);
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buf.writeUInt32BE(len, 0);
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buf.writeUInt32BE(type, 4);
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if (data) data.copy(buf, 8);
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buf.writeInt32BE(crc32(buf.slice(4, buf.length - 4)), buf.length - 4);
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return buf;
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};
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Parser.prototype._parseIHDR = function(data) {
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var width = data.readUInt32BE(0),
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height = data.readUInt32BE(4),
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depth = data[8],
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colorType = data[9], // 1 palette, 2 color, 4 alpha
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compr = data[10],
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filter = data[11],
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interlace = data[12];
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// console.log(' width', width, 'height', height,
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// 'depth', depth, 'colorType', colorType,
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// 'compr', compr, 'filter', filter, 'interlace', interlace
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// );
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if (depth != 8)
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throw new Error('Unsupported bit depth ' + depth);
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if (interlace != 0)
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throw new Error('Unsupported interlace method');
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this._colorType = colorType;
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this._compress.prepareInflate(compr);
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this._filter.prepare(width, height, filter);
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this._hasIHDR = true;
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this.emit('metadata', width, height);
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};
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Parser.prototype._packIHDR = function(width, height) {
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var buf = new Buffer(13);
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buf.writeUInt32BE(width, 0);
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buf.writeUInt32BE(height, 4);
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buf[8] = 8;
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buf[9] = 6; // colorType
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buf[10] = 0; // compression
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buf[11] = 0; // filter
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buf[12] = 0; // interlace
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return this._packChunk(TYPE_IHDR, buf);
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};
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Parser.prototype._parsePLTE = function(data) {
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var entries = Math.floor(data.length / 3);
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// console.log('Palette:', entries);
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for (var i = 0; i < entries; i++) {
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this._palette.push([
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data.readUInt8(i * 3),
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data.readUInt8(i * 3 + 1),
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data.readUInt8(i * 3 + 2 ),
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0xff
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]);
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}
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};
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Parser.prototype._parseTRNS = function(data) {
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// palette
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if (this._colorType == 3) {
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if (this._palette.length == 0)
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throw new Error('Transparency chunk must be after palette');
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if (data.length > this._palette.length)
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throw new Error('More transparent colors than palette size');
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for (var i = 0; i < this._palette.length; i++)
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this._palette[i][3] = i < data.length ? data.readUInt8(i) : 0xff;
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}
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// for colorType 0 (grayscale) and 2 (rgb)
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// there might be one gray/color defined as transparent
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};
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Parser.prototype._parseGAMA = function(data) {
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this.emit('gamma', data.readUInt32BE(0) / 100000);
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};
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Parser.prototype._parseIDAT = function(data) {
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if (this._colorType == 3 && this._palette.length == 0)
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throw new Error('Expected palette not found');
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this._compress.writeInflate(data);
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};
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Parser.prototype._packIDAT = function(data) {
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return this._packChunk(TYPE_IDAT, data);
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};
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Parser.prototype._parseIEND = function(data) {
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// no more data to inflate
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this._compress.endInflate();
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this._hasIEND = true;
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};
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Parser.prototype._packIEND = function() {
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return this._packChunk(TYPE_IEND, null);
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};
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// prepare crc table as in PNG Specification
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var crcTable = [];
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for (var i = 0; i < 256; i++) {
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var c = i;
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for (var j = 0; j < 8; j++) {
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if (c & 1) {
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c = 0xedb88320 ^ (c >>> 1);
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} else {
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c = c >>> 1;
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}
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}
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crcTable[i] = c;
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}
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function crc32(buf) {
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var crc = -1;
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for (var i = 0; i < buf.length; i++) {
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crc = crcTable[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);
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}
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return crc ^ -1;
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}
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