Drawing Tools > The Image Overlay

The Image Overlay

When you draw on an image, the drawing is not applied directly to the image. Instead, drawing elements are placed in overlay planes which float above the image. By way of analogy, you can imagine that each element you draw is drawn on a separate piece of transparent film that is placed in a stack over the image. Because each element resides on a separate piece of film, you can easily change the order of elements in the stack so that some elements appear to be in front of others, you can remove elements entirely from the stack and you can edit individual elements in the stack without affecting the other elements or the image itself.

Because the overlay is not actually part of the image data, if you want to export or replay an image with overlay information, you must first apply the overlay to the image with the Overlay Apply to Image Command (see The Overlay Apply to Image Command). Note that once you apply the overlay to the image, it becomes a permanent part of the image. You will not then be able to change the drawing elements or recover the portions of the image obscured by them.

The commands relating to the ordering and display of overlay elements are discussed in Overlay Functions.