In the nightly build, and possibly (I'm not sure) the 3.3.8 release, the autostretch button should now toggle auto-stretch--either giving you a stretched non-linear image, or when pressed again giving you a linear, usually very dark, view. The initial view depends on how you set the "EKOS --> options - -> FITS --> Auto Stretch" checkbox.
So, if you see a pretty black image, after pressing the autostretch button you should see a stretched (normal?) image, and then after hitting it again should go back to the pretty dark image, and so on. That would be "working as intended". Previously hitting the button didn't toggle it, but rather just somehow stretched it again.
If what you're seeing is not a linear view, but literally a black image, and you exposed in a way that the linear image should show stars, please try this:
Please take the saved .fits file and make sure it shows the same symptoms (i.e. use the "File --> Open FITS" command to load it).
Please then upload that file somewhere like dropbox or google drive where I can access it, and I'll take a look.
Please also say what type of camera, exposure, gain etc you are using.
Thank for you report,
PS I don't know if the log would have told us much in this case anyway, however, I wanted to mention that it doesn't appear that you have much logging enabled.
To log you need to enable some checkboxes, which you get in the main ekos window, by clicking the "Logs" button. In this case I might have checked Capture and FITS, but
I think just doing what I described above will be sufficient.
I built the git source a few days ago.
OK. So the behaviour changed? Now it's a toggle?
Previously if I had auto-stretch checked and if I hit auto stretch again, the displayed image was stretched more.
Is there any way we can specify the amount of auto-stretch applied?
Re making it stretch more: that's in my near-term plans (e.g. being able to specify the shadows, highlights and midtones), thought the exact UI hasn't yet been defined.
Before that's done, I supposed you could play with the histogram sliders, though those may or may not play well with the current stretch.
My new code/UI that allows you to modify the automatic stretch is now available. You can 'git pull' it from the main KStars git repository, and I imagine it will be in the nightly builds soon.
Hopefully the UI will be obvious when looking at the FitsViewer (there are now sliders and buttons on the bottom of the window).