There is an UI issue with shared settings when changing jpg/png/gif modes.
Example:
1. load & process jpg or have jpg mode selected from previous session (jpg does not support transparency)
2. switch to png & work with png
When we switch from jpg to png the UI keeps "blend" even if we normally have "keep transparency" selected. If we are not careful we will have to redo our work.
For now user fix is to correct transparency each time we change jpg/png/gif mode or restart RIOT.
Suggestion: RIOT should remember transparency settings for each mode separately.