sky

the sky calendar saves one dashcam still a day. this takes each one and measures the sky in it.

first it works out how high the sun was when the photo was taken. the photos don't save a location, so it assumes boise.

then it looks for the sky: smooth patches near the top of the frame, under the sun visor. during the day they have to be blue, and at twilight they have to be bright. that rule is because of a parking garage. a lot of my drives start under its roof, and the bright opening at the end looks a lot like sky. the catch is that a white overcast sky looks exactly like that opening too, so overcast days get skipped (sorry, overcast days).

asphalt is close enough to gray that the road works as a gray card for fixing the color, but only during the day. street lights tint it orange at night. brightness is whatever the camera picked after auto exposure, so a sky before sunrise can look lighter than it felt. sky/road compares the sky with the road in the same frame, which exposure doesn't change.

the crops only keep sky pixels. streets, cars and plates are see-through.

the script is telemetry/sky.py.