how to know this image is jpg or png iphone

Question

i will like to pick an images from UIImagepicker, there are PNG and JPG format in camera roll.

and i need to convert it into NSData. However i need to know if this images is UIImageJPEGRepresentation or UIImagePNGRepresentation so i could convert it.

UIImage *orginalImage = [info objectForKey:UIImagePickerControllerOriginalImage];    
    [picker dismissViewControllerAnimated:YES completion:nil];
    NSData *orgData = UIImagePNGRepresentation(orginalImage);

Pelion

Answer 1

You shouldn't know or care what the internal representation of images in the camera roll is. The methods you mentioned UIImageJPEGRepresentation and UIImagePNGRepresentation return you representations of the camera roll image. It's up to you to pick which representation you want to use.

To summarize:

NSData * pngData = UIImagePNGRepresentation(originalImage);

Will return you the image representation in an NSData object, with the format PNG.

Wellman

Sometimes you have to care, because if you make UIImageJPEGRepresentation from jpeg image, you might compress unnecessarily already compressed image (lose quality and processing time). For example, you might need the picked image to be further processed by library which accepts jpeg only. – Imbecility

Answer 2

When the delegate method imagePickerController:didFinishPickingMediaWithInfo: for UIImagePickerController is called, you get the asset URL for the particular photo picked.

[info valueForKey:UIImagePickerControllerReferenceURL]

Now this URL can be used to access the asset in the ALAssetsLibrary. Then you would need a ALAssetRepresentation of that accessed asset. From this ALAssetRepresentation we can get the UTI for that image (http://developer.apple.com/library/ios/#DOCUMENTATION/FileManagement/Conceptual/understanding_utis/understand_utis_conc/understand_utis_conc.html)

Maybe the code would make it a bit clearer :

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
  if (!(picker.sourceType == UIImagePickerControllerSourceTypeCamera)) {
    NSLog(@"User picked image from photo library");
    ALAssetsLibrary *library = [[[ALAssetsLibrary alloc] init] autorelease];
    [library assetForURL:[info valueForKey:UIImagePickerControllerReferenceURL] resultBlock:^(ALAsset *asset) {
      ALAssetRepresentation *repr = [asset defaultRepresentation];
      if ([[repr UTI] isEqualToString:@"public.png"]) {
        NSLog(@"This image is a PNG image in Photo Library");
      } else if ([[repr UTI] isEqualToString:@"public.jpeg"]) {
        NSLog(@"This image is a JPEG image in Photo Library");
      }
    } failureBlock:^(NSError *error) {
      NSLog(@"Error getting asset! %@", error);
    }];
  }
}

As the UTI explains, this should be a sure shot answer to how the image is stored in the photo library.

Trestlework

Answer 3

in Swift 2.2

func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
    if (!(picker.sourceType == UIImagePickerControllerSourceType.Camera)) {
        let assetPath = info[UIImagePickerControllerReferenceURL] as! NSURL
        if assetPath.absoluteString.hasSuffix("JPG") {

        } else {

        }

Depredation