pngjs-image
Version:
JavaScript-based PNG image encoder, decoder, and manipulator
217 lines (184 loc) • 4.16 kB
JavaScript
// Copyright 2015 Yahoo! Inc.
// Copyrights licensed under the Mit License. See the accompanying LICENSE file for terms.
var units = require('../utils/constants').offsetUnits;
/**
* @class oFFs
* @module PNG
* @submodule PNGChunks
*/
module.exports = {
/**
* Gets the sequence
*
* @method getSequence
* @return {int}
*/
getSequence: function () {
return 145;
},
/**
* Gets the offset for horizontal units
*
* @method getX
* @return {int}
*/
getX: function () {
return this._x || 0;
},
/**
* Sets the offset for horizontal units
*
* @method setX
* @param {int} x Horizontal units
*/
setX: function (x) {
this._x = x;
},
/**
* Gets the offset for vertical units
*
* @method getY
* @return {int}
*/
getY: function () {
return this._y || 0;
},
/**
* Sets the vertical number of pixel per unit
*
* @method setY
* @param {int} y Vertical units
*/
setY: function (y) {
this._y = y;
},
/**
* Gets the unit identifier
*
* @method getUnit
* @return {int}
*/
getUnit: function () {
return this._unit || 0;
},
/**
* Sets the unit identifier
*
* @method setUnit
* @param {int} unit Unit identifier
*/
setUnit: function (unit) {
if ([units.PIXEL, units.MICROMETER].indexOf(unit) === -1) {
throw new Error('Unit identifier ' + unit + ' is not valid.');
}
this._unit = unit;
},
/**
* Is unit in pixel?
*
* @method isUnitInPixel
* @return {boolean}
*/
isUnitInPixel: function () {
return (this._unit === units.PIXEL);
},
/**
* Is unit in micrometer?
*
* @method isUnitInMicroMeter
* @return {boolean}
*/
isUnitInMicroMeter: function () {
return (this._unit === units.MICROMETER);
},
/**
* Parsing of chunk data
*
* Phase 1
*
* @method parse
* @param {BufferedStream} stream Data stream
* @param {int} length Length of chunk data
* @param {boolean} strict Should parsing be strict?
* @param {object} options Decoding options
*/
parse: function (stream, length, strict, options) {
// Validation
if (strict && (this.getFirstChunk(this.getType(), false) !== null)) {
throw new Error('Only one ' + this.getType() + ' is allowed in the data.');
}
if ((strict && (length !== 9)) || (length < 9)) {
throw new Error('The length of chunk ' + this.getType() + ' should be 9, but got ' + length + '.');
}
this.setX(stream.readInt32BE());
this.setY(stream.readInt32BE());
this.setUnit(stream.readUInt8());
},
/**
* Gathers chunk-data from decoded chunks
*
* Phase 5
*
* @static
* @method decodeData
* @param {object} data Data-object that will be used to export values
* @param {boolean} strict Should parsing be strict?
* @param {object} options Decoding options
*/
decodeData: function (data, strict, options) {
var chunks = this.getChunksByType(this.getType());
if (!chunks) {
return ;
}
if (strict && (chunks.length !== 1)) {
throw new Error('Not more than one chunk allowed for ' + this.getType() + '.');
}
data.offset = {
x: chunks[0].getX(),
y: chunks[0].getY(),
unit: chunks[0].getUnit()
};
},
/**
* Returns a list of chunks to be added to the data-stream
*
* Phase 1
*
* @static
* @method encodeData
* @param {Buffer} image Image data
* @param {object} options Encoding options
* @return {Chunk[]} List of chunks to encode
*/
encodeData: function (image, options) {
if (options.offset) {
var chunk = this.createChunk(this.getType(), this.getChunks());
if (options.offset.x !== undefined) {
chunk.setX(options.offset.x);
}
if (options.offset.y !== undefined) {
chunk.setY(options.offset.y);
}
if (options.offset.unit !== undefined) {
chunk.setUnit(options.offset.unit);
}
return [chunk];
} else {
return [];
}
},
/**
* Composing of chunk data
*
* Phase 4
*
* @method compose
* @param {BufferedStream} stream Data stream
* @param {object} options Encoding options
*/
compose: function (stream, options) {
stream.writeInt32BE(this.getX());
stream.writeInt32BE(this.getY());
stream.writeUInt8(this.getUnit());
}
};