mirror of
https://github.com/danbulant/pngjs
synced 2026-05-26 21:31:56 +00:00
103 lines
2.5 KiB
JavaScript
Executable file
103 lines
2.5 KiB
JavaScript
Executable file
'use strict';
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var util = require('util');
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var Stream = require('stream');
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var zlib = require('zlib');
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var Filter = require('./filter');
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var CrcStream = require('./crc');
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var constants = require('./constants');
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var Packer = module.exports = function(options) {
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Stream.call(this);
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this._options = options;
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options.deflateChunkSize = options.deflateChunkSize || 32 * 1024;
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options.deflateLevel = options.deflateLevel != null ? options.deflateLevel : 9;
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options.deflateStrategy = options.deflateStrategy != null ? options.deflateStrategy : 3;
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this.readable = true;
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};
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util.inherits(Packer, Stream);
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Packer.prototype.pack = function(data, width, height, gamma) {
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// Signature
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this.emit('data', new Buffer(constants.PNG_SIGNATURE));
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this.emit('data', this._packIHDR(width, height));
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if (gamma) {
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this.emit('data', this._packGAMA(gamma));
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}
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// filter pixel data
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//TODO {}
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var filter = new Filter(width, height, 4, 8, false, this._options, {});
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var filteredData = filter.filter(data);
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// compress it
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var deflate = zlib.createDeflate({
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chunkSize: this._options.deflateChunkSize,
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level: this._options.deflateLevel,
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strategy: this._options.deflateStrategy
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});
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deflate.on('error', this.emit.bind(this, 'error'));
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deflate.on('data', function(compressedData) {
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this.emit('data', this._packIDAT(compressedData));
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}.bind(this));
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deflate.on('end', function() {
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this.emit('data', this._packIEND());
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this.emit('end');
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}.bind(this));
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deflate.end(filteredData);
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};
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Packer.prototype._packChunk = function(type, data) {
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var len = (data ? data.length : 0);
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var 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) {
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data.copy(buf, 8);
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}
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buf.writeInt32BE(CrcStream.crc32(buf.slice(4, buf.length - 4)), buf.length - 4);
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return buf;
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};
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Packer.prototype._packGAMA = function(gamma) {
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var buf = new Buffer(4);
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buf.writeUInt32BE(Math.floor(gamma * 100000), 0); // TODO constant
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return this._packChunk(constants.TYPE_gAMA, buf);
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};
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Packer.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(constants.TYPE_IHDR, buf);
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};
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Packer.prototype._packIDAT = function(data) {
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return this._packChunk(constants.TYPE_IDAT, data);
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};
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Packer.prototype._packIEND = function() {
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return this._packChunk(constants.TYPE_IEND, null);
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};
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