FilterList.php

<?php
/**
 * Copyright (C) 2019-2020 Graham Breach
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/**
 * For more information, please contact <graham@goat1000.com>
 */

namespace Goat1000\SVGGraph;

class FilterList {
  private $graph;
  private $filters = [];

  public function __construct(&$graph)
  {
    $this->graph =& $graph;
  }

  /**
   * Creates a shadow
   */
  public function shadow($params)
  {
    $opts = [
      'offset_x' => 10, 'offset_y' => 10,
      'opacity' => 0.5, 'blur' => 3,
      'shadow_only' => false,
    ];
    if(is_array($params))
      $opts = array_merge($opts, $params);

    // matrix converts to black and sets opacity
    $o = new Number(min(max($opts['opacity'], 0.005), 1.0));
    $matrix = [
      'type' => 'matrix',
      'values' =>
        '0 0 0 0 0 ' .
        '0 0 0 0 0 ' .
        '0 0 0 0 0 ' .
        '0 0 0 ' . $o . ' 0',
    ];
    $matrix = $this->graph->element('feColorMatrix', $matrix);
    $offset = $blur = '';

    // offset positions the shadow
    $offsets = [
      'dx' => new Number($opts['offset_x']),
      'dy' => new Number($opts['offset_y']),
      'result' => 'res',
    ];
    if($offsets['dx']->value || $offsets['dy']->value)
      $offset = $this->graph->element('feOffset', $offsets);

    // blur the outline
    $gblur = [
      'stdDeviation' => new Number($opts['blur']),
      'result' => 'res',
    ];
    if($gblur['stdDeviation']->value > 0)
      $blur = $this->graph->element('feGaussianBlur', $gblur);

    // if there is no blur and no offset, there is no shadow
    if($blur === '' && $offset === '')
      return null;

    $content = $matrix . $offset . $blur;
    if(!$opts['shadow_only']) {
      $merged = $this->graph->element('feMergeNode', ['in' => 'res']) .
        $this->graph->element('feMergeNode', ['in' => 'SourceGraphic']);
      $content .= $this->graph->element('feMerge', null, null, $merged);
    }

    $filter = [
      'id' => $this->graph->newID(),
      'filterUnits' => 'userSpaceOnUse'
    ];

    return [
      'id' => $filter['id'],
      'content' => $this->graph->element('filter', $filter, null, $content),
    ];
  }

  /**
   * Adds a filter
   */
  public function add($type, $params = null)
  {
    $key = md5(serialize([$type, $params]));
    if(isset($this->filters[$key]))
      return $this->filters[$key]['id'];

    if(!method_exists($this, $type))
      throw new \InvalidArgumentException('Unknown filter: ' . $type);

    $result = $this->{$type}($params);
    if($result === null)
      return null;
    $this->filters[$key] = $result;
    return $result['id'];
  }

  /**
   * Adds the filters to the defs
   */
  public function makeFilters(&$defs)
  {
    foreach($this->filters as $filter)
      $defs->add($filter['content']);
  }
}