Question

My app will let users cut out things from photos. They’ll be able to either select a photo already in their iPhone’s photo library, or take a new one with the camera. From what I understand, UIImagePicker is the simplest way to accomplish picking a photo from the library or taking a new one. However, I also understand that it only provides basic image editing (zoom, crop). I want my image editing to allow for the creation of Bezier curves that, once all joined together, will cut out the enclosed area, saving it without the surrounding background.

The official apple documentation on UIImagePicker suggested that the AV Framework is required for providing custom image editing as opposed to the basic zoom and crop. So my first questions are:

1. Is the AV Framework indeed what I want to
   use?

2. Will it get used in conjunction with UIImagePicker (i.e., UIImagePicker is used to select the photo or take a new one, and then my AV Framework code takes over for the image editing)?

3. Can anyone offer good resources on getting started on learning the code for this process?

My final question is about the actual Bezier curve generation/manipulation. It appears that the Core Graphics Framework has support for this, but there is also the UIBezierPath object, which is apparently some kind of wrapper for the Core Graphics tools I would otherwise use.

So my final question: will I want to use the UIBezierPath object, or does what I previously described require more fine-grained control that UIBezierPath can’t provide, thereby forcing me to use the Core Graphics framework directly?

Thanks!

Answer 1

1. the AV Foundation allows you to talk to the camera, to configure it in various ways, and to receive a live feed from it. So it’s good for taking new pictures or movies, but not for selecting them from the camera roll or for editing them. You’d likely want to use the AV Foundation to replace the image capture duties that UIImagePicker supplies. Probably you’ll want to use a UIImagePicker with allowsEditing set to NO so as to be able to provide your own entirely separate editing interface.

2. no, it’s a different sort of task.

3. I’m unaware of any tutorials on this sort of thing, but the docs are pretty good. I’ve posted the whole stuff for capturing a live feed from the camera in answers like this one, not sure if that’s a more helpful way to see how some of the AV Foundation classes can be chained together?

What you’ll probably end up doing in order to edit an image is starting with a UIImage, creating a CoreGraphics bitmap context (which is something you can draw to), doing some sort of compositing to that and then converting the result into an image and saving it back out to the camera roll.

UIBezierPath is a wrapper over the Core Graphics stuff, but will probably do what you want. addClip can set a defined path to be the new clipping path on the current context, or you can use the CGPath property if you need to go a bit further afield than UIKit’s idea of a current context.