1: <?php
 2: /**
 3:  * Image effect for applying an unsharpmask.
 4:  *
 5:  * Copyright 2010-2012 Horde LLC (http://www.horde.org/)
 6:  *
 7:  * See the enclosed file COPYING for license information (LGPL). If you
 8:  * did not receive this file, see http://www.horde.org/licenses/lgpl21.
 9:  *
10:  * @author  Michael J. Rubinsky <mrubinsk@horde.org>
11:  * @package Image
12:  */
13: class Horde_Image_Effect_Im_Unsharpmask extends Horde_Image_Effect
14: {
15:     /**
16:      *
17:      * Valid parameters:
18:      *
19:      *  (float)radius - Thickness of the sharpened edge. Should be greater then
20:      *                  sigma (or 0, and imagick will attempt to auto choose).
21:      *                  In general, radius should be roughly output dpi / 150.
22:      *                  So for display purposes a radius of 0.5 is suggested.
23:      *
24:      *  (float)amount - Amount of the difference between original and the
25:      *                  blur image that gets added back to the original. Can be
26:      *                  thought of as the "strength" of the effect. Too high
27:      *                  may cause blocking of shadows and highlights. Given
28:      *                  a decimal value indicating percentage, e.g. 1.2 = 120%
29:      *
30:      *  (float)threshold - Determines how large the brightness delta between
31:      *                     adjacent pixels needs to be to sharpen the edge.
32:      *                     Larger values == less sharpening. Useful for
33:      *                     preventing noisy images from being oversharpened.
34:      *
35:      *  (integer)channel - Which channel to apply the sharpening to.
36:      *
37:      * @var array
38:      */
39:     protected $_params = array('radius' => 0.5,
40:                                'amount' => 1,
41:                                'threshold' => 0.05);
42: 
43:     public function apply()
44:     {
45:         /* Calculate appropriate sigma:
46:          * Determines how the sharpening is graduated away from
47:          * the center pixel of the sharpened edge. In general,
48:          * if radius < 1, then sigma = radius else sigma = sqrt(radius)
49:          */
50:         $this->_params['sigma'] = ($this->_params['radius'] < 1) ?
51:                 $this->_params['radius'] : sqrt($this->_params['radius']);
52: 
53:         $this->_image->addPostSrcOperation("-unsharp {$this->_params['radius']}x{$this->_params['sigma']}+{$this->_params['amount']}+{$this->_params['threshold']}");
54: 
55:         return true;
56:     }
57: 
58: }