public void paintAt(int x, int y, Pixel brushColor, int brush_size) {
		
		//push current fraem into stack
		undo_frames.push(current.copy());
		
		current.suspendNotifications();
		
		for (int xpos=x-brush_size+1; xpos <=x+brush_size-1; xpos++) {
			for (int ypos=y-brush_size+1; ypos <=y+brush_size-1; ypos++) {
				if (xpos >= 0 &&
					xpos < current.getWidth() &&
					ypos >= 0 &&
					ypos < current.getHeight()) {
					current.setPixel(xpos, ypos, brushColor);
				}
			}
		}
		current.resumeNotifications();
		
		
	}