Improve Image clone

lime/graphics/Image.hx

@@ -158,6 +158,7 @@ class Image {
 	public function clone ():Image {
 		
 		var image = new Image (buffer.clone (), offsetX, offsetY, width, height, null, type);
+		image.dirty = dirty;
 		return image;
 		
 	}

lime/graphics/ImageBuffer.hx

@@ -108,6 +108,8 @@ class ImageBuffer {
 		}
 		#end
 		
+		buffer.bitsPerPixel = bitsPerPixel;
+		buffer.format = format;
 		buffer.premultiplied = premultiplied;
 		buffer.transparent = transparent;
 		return buffer;