Fixed content image transparency

Author: radkovo

src/main/java/org/fit/cssbox/layout/ContentImage.java

@@ -201,7 +201,7 @@ public BufferedImage getBufferedImage()
         if (container == null)
             waitForLoad();
 
-        BufferedImage img = new BufferedImage(getIntrinsicWidth(), getIntrinsicHeight(), BufferedImage.TYPE_INT_RGB);
+        BufferedImage img = new BufferedImage(getIntrinsicWidth(), getIntrinsicHeight(), BufferedImage.TYPE_INT_ARGB);
         Graphics2D g = img.createGraphics();
         g.drawImage(image, null, null);
         g.dispose();