I have a photo displayed on an iPhone. I would like to lower brightness of the photo at first, and when the user touches the photo, I would like to raise the brightness of the rectangular region near where the user touched, like this:
www.cottagearts.net/tut_images/tut_cropping_pse_06.jpg
Could anyone point me to a simple way of doing this?
While you can't actually adjust the brightness of the screen, you can put a semi-transparent image on the screen. I'd paint everywhere but where the user touched with an color that is black, but has X transparency, which is exactly what that image is showing that you linked to.
I'm no expert, but I've been trying to do something similar. You could implement this with layers. As Malfist suggested, you could make a black layer with a certain opacity and may the clicked part of it fully transparent or somesuch. Another option would be to do some image processing. I found an article here that I think will handle my highlighting issue:
http://arstechnica.com/apple/news/2009/03/iphone-dev-basic-image-processing-package.ars
