imagesavealpha() in Element\Image

Author: samsullivan

src/PhpWord/Element/Image.php

@@ -335,6 +335,10 @@ public function getImageStringData($base64 = false)
         // Read image binary data and convert to hex/base64 string
         if ($this->sourceType == self::SOURCE_GD) {
             $imageResource = call_user_func($this->imageCreateFunc, $actualSource);
+            if ($this->imageType === 'image/png') {
+                // PNG images need to preserve alpha channel information
+                imagesavealpha($imageResource, true);
+            }
             ob_start();
             call_user_func($this->imageFunc, $imageResource);
             $imageBinary = ob_get_contents();