I really love the cage transform tool in the GIMP. It was first developed by Google Summer of Code student Michael Muré in 2010 and finished by Gimp developer Alexia Death.
It allows you to define an area within an image (in my case, the four corners of the whiteboard frame) and drag on those points to stretch the image out. For this whiteboard photo that was taken at an angle, this process resulted in a straightened-out image of the whiteboard. (I followed up with a Difference of Gaussians cleanup that Garrett taught me a while back 🙂 )
It’s a pretty magical tool. Give it a try!
Such tool is integrated in CamScanner in Android, which I use pretty often. Take photo – apply this tool – send as pdf — all in one step.
https://play.google.com/store/apps/details?id=com.intsig.camscanner&feature=search_result#?t=W251bGwsMSwyLDEsImNvbS5pbnRzaWcuY2Ftc2Nhbm5lciJd
He, I finished it myself =)
I’m happy that you like it =)
Ah, sorry about that! The Libre Graphics World article had credited it that way so that’s where I got it. Thanks for the correction! Amazing tool!
I’m finding cage transform rather handy too. Just discovered it in 2.8 RC1 a couple of days ago.
Garrett suggested on the Twitterz:
“I usually use perspective transform in reverse (“Corrective”) mode, with guidelines on. Then, make the corners match up!”