Replace boolean cast to be able to disable frame, aspect ratio, trans…

…parency or constrain only in view.xml

If you set frame to false in view.xml the code would cast it to true because (bool)'false' is equal to true. By using the filter_var function the cast to boolean is done correctly.

app/code/Magento/Catalog/Model/Product/Image.php

@@ -278,7 +278,7 @@ public function getQuality()
      */
     public function setKeepAspectRatio($keep)
     {
-        $this->_keepAspectRatio = (bool)$keep;
+        $this->_keepAspectRatio = filter_var($keep, FILTER_VALIDATE_BOOLEAN);
         return $this;
     }
 
@@ -288,7 +288,7 @@ public function setKeepAspectRatio($keep)
      */
     public function setKeepFrame($keep)
     {
-        $this->_keepFrame = (bool)$keep;
+        $this->_keepFrame = filter_var($keep, FILTER_VALIDATE_BOOLEAN);
         return $this;
     }
 
@@ -298,7 +298,7 @@ public function setKeepFrame($keep)
      */
     public function setKeepTransparency($keep)
     {
-        $this->_keepTransparency = (bool)$keep;
+        $this->_keepTransparency = filter_var($keep, FILTER_VALIDATE_BOOLEAN);
         return $this;
     }
 
@@ -308,7 +308,7 @@ public function setKeepTransparency($keep)
      */
     public function setConstrainOnly($flag)
     {
-        $this->_constrainOnly = (bool)$flag;
+        $this->_constrainOnly = filter_var($flag, FILTER_VALIDATE_BOOLEAN);
         return $this;
     }