The picamera object isn't thread safe; I have now wrapped all access
in context managers that acquire the BaseCamera.lock
I also added an endpoint to reset the LST without auto-gain.
When testing the UI I noticed that the different recalibrate routines
don't use locks properly, so they try to run
concurrently.
This commit isn't tested yet...
The previous "auto calibrate" button for the camera relied on a
combination of the built-in autoexposure/AWB and
some JPEG-based tweaks to get the exposure settings right.
This often led to confusing results, e.g. oscillating between green and
pink images.
I have rewritten the auto-exposure code to adjust gain and shutter
speed based on the raw image. This seems to be
very reliable, at the expense of being quite slow. That's a price I'm
happy to pay.
I have replaced both the camera's auto white balance and my
JPEG-based AWB hack with a single-shot AWB method that
looks at the raw image.
