Group a collection of drawn objects to have a single opacity

[XylemFlow 6]

I need to be able to draw several objects to a form or TImage TCanvas, including lines, circles, polygons, text, etc and have them drawn as a group with a single opacity. If I draw them separately then it won't look correct where they overlap.

I currently do this by drawing the objects to an offscreen TBitmap canvas with full opacity and then drawing the TBitmap to my form or TImage TCanvas with the opacity I want. However, this is slower and uses more memory. I'd also like to use Skia in future, but I understand that drawing to offscreen bitmaps is slower since it doesn't use the GPU.

Is there a method to group objects in this way in default FMX or Skia without using an offscreen bitmap? 

[Keesver 20]

You can add all objects to the same TLayout and then control the opacity from this TLayout.

[Rollo62 502]

All objects under same layout and managing layers and groups with TLayout: Yes, definitively.

Not sure what kind of "opacity" you need, but you could also put finally a TRectangle as cover over all, with Align := Contents,

and set HitTest := False, Stroke.Kind := None,  File.Color := White (or Black depending on your design), and set Opacity as you desire.
This will "grey out" the underlying objects, while they are still active.

 

[XylemFlow 6]

Unfortunately I need to draw everything directly on a single TCanvas. I cannot do it by layering controls on top of each other. One reason is because I need to export the resulting image. By sharing the same opacity I mean that they should be semi transparent and so show previously drawn objects underneath