fix: remove transparency of PNG images without a .png extension, fixe… (

#9632)

fix: remove transparency of PNG images without a .png extension, fixes #9621

lib/ProductOpener/Images.pm

@@ -850,8 +850,8 @@ sub process_image_upload ($product_id, $imagefield, $user_id, $time, $comment, $
 		$source->AutoOrient();
 		$source->Strip();    #remove orientation data and all other metadata (EXIF)
 
-		# remove the transparency for PNG files
-		if ($extension eq "png") {
+		# remove the transparency when there is an alpha channel (e.g. in PNG files) by adding a white background
+		if ($source->Get('matte')) {
 			$log->debug("png file, trying to remove the alpha background") if $log->is_debug();
 			my $bg = Image::Magick->new;
 			$bg->Set(size => $source->Get('width') . "x" . $source->Get('height'));