yahoo/pngjs-image

// Copyright 2015 Yahoo! Inc.
// Copyrights licensed under the Mit License. See the accompanying LICENSE file for terms.

var units = require('../utils/constants').physicalUnits;

/**
 * @class pHYs
 * @module PNG
 * @submodule PNGChunks
 */
module.exports = {

    /**
     * Gets the sequence
     *
     * @method getSequence
     * @return {int}
     */
    getSequence: function () {
        return 140;
    },


    /**
     * Gets the horizontal number of pixel per unit
     *
     * @method getXPixelPerUnit
     * @return {int}
     */
    getXPixelPerUnit: function () {
        return this._xPPU || 1;
    },

    /**
     * Sets the horizontal number of pixel per unit
     *
     * @method setXPixelPerUnit
     * @param {int} ppu Pixel per unit
     */
    setXPixelPerUnit: function (ppu) {
        this._xPPU = ppu;
    },


    /**
     * Gets the vertical number of pixel per unit
     *
     * @method getYPixelPerUnit
     * @return {int}
     */
    getYPixelPerUnit: function () {
        return this._yPPU || 1;
    },

    /**
     * Sets the vertical number of pixel per unit
     *
     * @method setYPixelPerUnit
     * @param {int} ppu Pixel per unit
     */
    setYPixelPerUnit: function (ppu) {
        this._yPPU = ppu;
    },


    /**
     * 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.UNKNOWN, units.METER].indexOf(unit) === -1) {
            throw new Error('Unit identifier ' + unit + ' is not valid.');
        }
        this._unit = unit;
    },


    /**
     * Is unit unknown?
     *
     * @method isUnitUnknown
     * @return {boolean}
     */
    isUnitUnknown: function () {
        return (this._unit === units.UNKNOWN);
    },

    /**
     * Is unit in meter?
     *
     * @method isUnitInMeter
     * @return {boolean}
     */
    isUnitInMeter: function () {
        return (this._unit === units.METER);
    },


    /**
     * 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.setXPixelPerUnit(stream.readUInt32BE());
        this.setYPixelPerUnit(stream.readUInt32BE());
        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.physicalSize = {
            xPixelPerUnit: chunks[0].getXPixelPerUnit(),
            yPixelPerUnit: chunks[0].getYPixelPerUnit(),
            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.physicalSize) {

            var chunk = this.createChunk(this.getType(), this.getChunks());

            if (options.physicalSize.xPixelPerUnit !== undefined) {
                chunk.setXPixelPerUnit(options.physicalSize.xPixelPerUnit);
            }
            if (options.physicalSize.yPixelPerUnit !== undefined) {
                chunk.setYPixelPerUnit(options.physicalSize.yPixelPerUnit);
            }
            if (options.physicalSize.unit !== undefined) {
                chunk.setUnit(options.physicalSize.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.writeUInt32BE(this.getXPixelPerUnit());
        stream.writeUInt32BE(this.getYPixelPerUnit());
        stream.writeUInt8(this.getUnit());
    }
};