Students often use their cell phone camera to make copies of each others' notes and then they come to me to print them. Printing such images as is would be a waste of toner. Removing the perspective and adjusting colors to have real white background is time consuming. They usually cannot do it and I usually don't want to do it for them. They also don't like when I tell them that the price is multiplied by three if I print the photos as they are. (The service is non-profit.)
Is there any desktop application (Win7) or GIMP plugin or online service that can do this specific task automatically?
Usual image properties: The A4 document is on the floor, or on a table. Pure white paper (or patterned paper) has writing on it with pen. Sometimes it is a photo of a printed PDF (Yeah!). Sometimes they use red and blue and black pen on the same page. The lighting is usually not horrible (but sometimes they make it in a pub using flash).
(Don't mind the poor resolution of the sample image, they are usually better.)