ol-ext/filter/SVGFilter.js

A set of cool extensions for OpenLayers (ol) in node modules structure

/*	Copyright (c) 2016 Jean-Marc VIGLINO, 
  released under the CeCILL-B license (French BSD license)
  (http://www.cecill.info/licences/Licence_CeCILL-B_V1-en.txt).
*/

import ol_filter_Base from './Base.js'

/** Add a canvas Context2D SVG filter to a layer
 * @see https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/filter
 * @constructor
 * @requires ol.filter
 * @extends {ol_filter_Base}
 * @param {ol_ext_SVGFilter|Array<ol_ext_SVGFilter>} filters
 */
var ol_filter_SVGFilter = class olfilterSVGFilter extends ol_filter_Base {
  constructor(filters) {
    super();
    this._svg = {};
    if (filters) {
      if (!(filters instanceof Array))
        filters = [filters];
      filters.forEach(function (f) {
        this.addSVGFilter(f);
      }.bind(this));
    }
  }
  /** Add a new svg filter
   * @param {ol.ext.SVGFilter} filter
   */
  addSVGFilter(filter) {
    var url = '#' + filter.getId();
    this._svg[url] = 1;
    this.dispatchEvent({ type: 'propertychange', key: 'svg', oldValue: this._svg });
  }
  /** Remove a svg filter
   * @param {ol.ext.SVGFilter} filter
   */
  removeSVGFilter(filter) {
    var url = '#' + filter.getId();
    delete this._svg[url];
    this.dispatchEvent({ type: 'propertychange', key: 'svg', oldValue: this._svg });
  }
  /**
   * @private
   */
  precompose() {
  }
  /**
   * @private
   */
  postcompose(e) {
    var filter = [];
    // Set filters
    for (var f in this._svg) {
      filter.push('url(' + f + ')');
    }
    filter = filter.join(' ');
    var canvas = document.createElement('canvas');
    canvas.width = e.context.canvas.width;
    canvas.height = e.context.canvas.height;
    canvas.getContext('2d').drawImage(e.context.canvas, 0, 0);
    // Apply filter
    if (filter) {
      e.context.save();
      e.context.clearRect(0, 0, canvas.width, canvas.height);
      e.context.filter = filter;
      e.context.drawImage(canvas, 0, 0);
      e.context.restore();
    }
  }
}

export default ol_filter_SVGFilter