add gamma correct option

With a new option on the main class, we will able to tell if we want gamma correction.

When you use this library and rescale a image, the image's colors tends to not be keeped, this is caused by the image gamma correction applied before and after the proccessing.

Author: lefuturiste

lib/ImageResize.php

@@ -47,7 +47,8 @@ class ImageResize
     protected $source_h;
 
     protected $source_info;
-
+    
+    protected $gamma_correct = true;
 
     protected $filters = [];
 
@@ -286,7 +287,9 @@ public function save($filename, $image_type = null, $quality = null, $permission
 
         imageinterlace($dest_image, $this->interlace);
 
-        imagegammacorrect($this->source_image, 2.2, 1.0);
+        if ($this->gamma_correct) {
+            imagegammacorrect($this->source_image, 2.2, 1.0);
+        }
 
         if( !empty($exact_size) && is_array($exact_size) ) {
             if ($this->getSourceHeight() < $this->getSourceWidth()) {
@@ -312,7 +315,9 @@ public function save($filename, $image_type = null, $quality = null, $permission
             $this->source_h
         );
 
-        imagegammacorrect($dest_image, 1.0, 2.2);
+        if ($this->gamma_correct) {
+            imagegammacorrect($dest_image, 1.0, 2.2);
+        }
 
 
         $this->applyFilter($dest_image);