Java Graphics2D transparent background

Question

I have a Graphics2D object and I want to set up the background of the object. It has a setBackground method, which has a Color parameter. This way I can set the color of the background.

My question is: how can I set the transparency of the background of the object? Can I somehow tell it to be completely transparent? Can I somehow tell it to be completely opaque? Can I somehow tell it to have 0.8 transparency/opacity? How can I set these values?

I have seen that there are int predefined values called TRANSLUCENT and OPAQUE, but I am not sure how can I use them.

Maybe the correct usage is to call the constructor of Color with an int parameter?

Answer 1

You can construct a Color object by specifying a transparency. For example the following code constructs a RED color with 50% transparency

Color c=new Color(1f,0f,0f,.5f ); 

Answer 2

You can call the constructor of Color in the following way:

Color c = new Color(r,g,b,a); 

where a is the alpha (transparency) value.

As with all Java classes, you can find this information in the official API: http://docs.oracle.com/javase/7/docs/api/java/awt/Color.html

It's a really good resource and can spare you waiting for an answer on here.