Bug report

Describe the bug

See https://forum.image.sc/t/small-bug-rendered-rgb-export-does-not-use-gamma-setting/106202.

To Reproduce

Steps to reproduce the behavior:

1. Open any image.
2. Change Viewer gamma in Brightness and contrast to something else than 1.
3. File > Export Images > Rendered RGB (with overlay): the exported image has still a gamma of 1.

Expected behavior

The Rendered RGB image should take the viewer gamma into account.

Desktop:

• OS: macOS but very likely to be any OS.
• QuPath Version: 0.5.1 and 0.6.0-rc3