Greetings,Are you asking how to make a specific color transparent?
No, I want to change the background in a photo so that it is all white so the person in photo looks like he is standing in front of a plain white wall.
iPhoto is limited in that function.You can download a free program called Gimp from the following link: http://gimp.lisanet.de/Website/Download.html
The instructions to remove the background using Gimp are found at the following site: http://www.photonur.com/changingphotobackground.htm
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