Cropping image

Depends on the type of cropping you want to achieve. If you want users to be able to crop an image they've taken with the camera or picked from the gallery, you can set the allowsEditing property to YES on the UIImagePickerController, like this:

UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
    imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
} else {
    imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
}
imagePicker.allowsEditing = YES;

In that case, you'll also have to grab the edited image, not the original one in - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info like this:

UIImage *image = info[UIImagePickerControllerEditedImage];

But if you want to crop an UIImage you already have somewhere in your code, then this tutorial/example should help.