The 'Setopacity' method

Argument: Scalar number between 0.0 and 1.0
Result: None

Valid for: Image

The Setopacity method allows you to specify that an image is semi-transparent. Making an image semi-transparent means that, when you place it on top of another image using the Overlay method, the background image will still be partially visible through the foreground image. The method takes a single argument, which is a number between 0.0 (completely transparent) to 1.0 (fully opaque, i.e. the background is not visible at all).

Note that some file formats, such as PNG, allow specific parts of the image to be transparent. In this case you don't need to set the opacity directly.