Question

I’ve got a UIImagePickerController letting the user pick an image out of the image library, and am getting its results via the didFinishPickingMediaWithInfo method.

I need to be able to save the resulting image to disk (in the app’s documents folder), and reload it later.

The issue is that I can’t tell whether to store it as a PNG or JPEG. I can’t just always store it as a PNG, because for larger photos it’s interminably slow (not to mention then I have to deal with storing the image orientation separately). I can’t just always store it as a JPEG, because in some cases the images have transparency, which will get lost if I do that.

I’ve examined the UIImagePickerControllerMediaType key in the info dictionary returned by the image picker, and regardless of whether I’ve selected a PNG or JPEG, what gets returned is "image.public".

So…

Is there some way to know whether the user has chosen a PNG? Maybe some method of just checking if the image has any transparency or something?

Thanks.

Answer 1

in the dictionary the key UIImagePickerControllerReferenceURL will give you informations about the type

(gdb) po info

{
    UIImagePickerControllerMediaType = "public.image";
    UIImagePickerControllerOriginalImage = "<UIImage: 0x5cfd00>";
    UIImagePickerControllerReferenceURL = "assets-library://asset/asset.JPG?id=EFC44C3C-9C82-4669-924B-A2B9DE6F1F45&ext=JPG";
}

In this case it is a jpg as shown by ext=JPG