Good day, dear habravchane. On the Internet, I met one miniature and very interesting Bash script. Using ImageMagick, he handles photos of a white tutorial in an amazing way, cleansing up the "contents" of everything that is superfluous:
Before:

')
After:

How to use:
./whiteboardClean.sh {name of input file} {name of file to output to}
./whiteboardClean.sh example1.jpg output1.png
And to create this script, the author pushed the post "
How to clean up photos of whiteboards with Gimp ".
GistThank you all for your attention.
UPD: dshost
habrauzer made a web service that performs the same task -
http://api.o2b.ru/whiteboardcleaner