I have a projector, which doesn't come with horizontal keystone correction built in, only vertical correction.<p>I've seen that it is possible to do it with xrandr, using the --transform parameter, but needs matrix coordinates and I'm lost. That deserves a GUI, but ARandR doesn't support it.<p>I've also checked MapMap project, but seems that v4l2 virtual video device is not well recognized to use it as source.<p>Do you know any other alternative to transform the screen?
<a href="https://askubuntu.com/" rel="nofollow">https://askubuntu.com/</a> seems a better match for that specific problem.