Capturing Screenshot of UIVIew with multiple CALayers displays white background while save image in gallery

Question

I have a UIView with different CALayers with different size.

When I am trying to save UIView as image to gallery it looses its transparency:

My code is:

- (UIImage *) imageWithView:(UIView *)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, [UIScreen mainScreen].scale);
    [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

//Getting image

 UIImage *img=[self imageWithView:MainView];
 UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil);

Note:When I debug the code, it displays transparent image, but when I see in gallery it displays with white Background

Answer 1

I've tried your code. You can try following implementation:

- (void)viewDidLoad {
    [super viewDidLoad];

    UIView *tmpView = [UIView new];
    tmpView.frame = self.view.bounds;
    tmpView.backgroundColor = [UIColor clearColor];
    [self.view addSubview:tmpView];

    UIImage *img = [self imageWithView:tmpView];
    [self saveInJPGFormat:img];
    [self saveInPNGFormat:img];
}

- (void)saveInJPGFormat:(UIImage *)image {
    UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
}

- (void)saveInPNGFormat:(UIImage *)image {
    NSData* imageData =  UIImagePNGRepresentation(image);
    UIImage* pngImage = [UIImage imageWithData:imageData];
    UIImageWriteToSavedPhotosAlbum(pngImage, nil, nil, nil);
}

- (UIImage *) imageWithView:(UIView *)view {
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, [UIScreen mainScreen].scale);
    [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

Your method saves as JPG to camera roll. JPGs aren't capable to keep alpha channel. Second method taken from https://stackoverflow.com/a/10279075/849616 saves image as PNG. I can open it and I can see through the image (alpha channel is saved).

BTW: ofc that's very dirty and quick code. In reality you should do a category on UIImage for these methods. Also keep MVC and either views&layers stick to storyboards or to separate UIView subclass.

Images from my photo gallery: Screen of preview so you're sure it's empty:

So the method is working.