Bug report

Describe the bug
As discussed at the hackathon with @zmikulski, being able to adjust the gamma of an image can be very important in some cases.

Also, mini viewers don't currently respond to any gamma changes.

See @saramcardle's post for more details: qupath/2022-qupath-hackathon#9

To Reproduce

1. Open an image
2. Choose View → Mini viewers... → Show mini viewer or View → Mini viewers... → Show channel viewer3.
3. Adjust the gamma value under the preferences

Expected behavior
Two things:

1. the gamma adjusts in the mini/channel viewer, to match the main image
2. it is possible for the user to see that the gamma is not 1 without having to search the preferences

Screenshots

Desktop (please complete the following information):

• OS: All
• QuPath Version: all up until v0.3.2 (current)