[Overlay] FR: Provide optional flag for `View#write_image` to include Overlays

[dphdave]

Following on from #904

Feature Request

There are many use-cases where it would be beneficial for View#write_image to provide an optional flag :overlay or similar so that developers can specify that the overlay should be included in the saved image.

[thomthom]

@dphdave can you list some of these use cases please? Helps with the context.

[Fredosixx]

You can overlay Labels, legends and other 2D decoration elements for the output images. As you know, these elements are difficult to manage for 2D view with geometry or base elements (Lines for arrows, Text, dimensions, etc....). With overlays, it is much much easier, as you can draw text in any size, position graphical elements in the model view, etc..... In addition, there is no pollution of the main model since this is transient drawing only used for capturing images.

Indeed, this also opens a lot of possibilities for Animation (I would benefit of it in Animator).

The floag could be for Overlays but also for Tool drawings (i.e. what is produced in Tool#draw()).