added colorize method

src/Intervention/Image/Exception/ColorizeOutOfBoundsException.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Intervention\Image\Exception;
+
+class ColorizeOutOfBoundsException extends \OutOfBoundsException
+{
+    # nothing to override
+}

src/Intervention/Image/Image.php

@@ -1275,6 +1275,37 @@ class Image
         return $this;
     }
 
+    /**
+     * Apply colorize filter to current image
+     *
+     * @param  integer $red
+     * @param  integer $green
+     * @param  integer $blue
+     * @return Image
+     */
+    public function colorize($red, $green, $blue, $alpha = 0)
+    {
+        if (($red < -100 || $red > 100) || 
+            ($green < -100 || $green > 100) || 
+            ($blue < -100 || $blue > 100) || 
+            ($alpha < -100 || $alpha > 100)) {
+                throw new Exception\ColorizeOutOfBoundsException(
+                    'Colorize levels must be between -100 and +100'
+            );
+        }
+
+        // normalize colorize levels
+        $red = round($red * 2.55);
+        $green = round($green * 2.55);
+        $blue = round($blue * 2.55);
+        $alpha = round($alpha * 2.55);
+
+        // apply filter
+        imagefilter($this->resource, IMG_FILTER_COLORIZE, $red, $green, $blue, $alpha);
+
+        return $this;
+    }
+
     /**
      * Apply blur filter on the current image
      *

tests/ImageTest.php

@@ -1577,6 +1577,23 @@ class ImageTest extends PHPUnit_Framework_Testcase
         $img->contrast(-101);
     }
 
+    public function testColorizeImage()
+    {
+        $img = $this->getTestImage();
+        $img->colorize(-100, 0, 100);
+        $img->colorize(100, -100, -100, 50);
+        $this->assertInstanceOf('Intervention\Image\Image', $img);
+    }
+
+    /**
+     * @expectedException Intervention\Image\Exception\ColorizeOutOfBoundsException
+     */
+    public function testColorizeOutOfBounds()
+    {
+        $img = $this->getTestImage();
+        $img->colorize(-101, 0, 0);
+    }
+
     public function testEncode()
     {
         // default encoding