Question

EDIT ANSWER:

- (UIImage*) maskImage:(UIImageView *)maskImage withMask:(UIImageView *)cropImage
{

    UIImage *image = nil;
    UIImage *imagePNG = nil;

    CGSize newImageSize = CGSizeMake(cropImage.frame.size.width, cropImage.frame.size.height);

    UIGraphicsBeginImageContextWithOptions(newImageSize, NO, 0.0); //retina res
    [self.viewForImg.layer renderInContext:UIGraphicsGetCurrentContext()];

    image = UIGraphicsGetImageFromCurrentImageContext();


    NSData *imgData =  UIImagePNGRepresentation ( image ); // get PNG representation
    imagePNG = [UIImage imageWithData:imgData]; // wrap UIImage around PNG representation
    UIGraphicsEndImageContext(); 
    return imagePNG;
}

i tried to screenshots my iphone screen to save a picture into my camera roll.
but encountered this error. anybody know if there is an issues with my code ?

May 22 14:13:34 unknown assetsd[281] <Error>: ImageIO: CGImageDestinationAddImage image parameter is nil
May 22 14:13:34 unknown assetsd[281] <Error>: ImageIO: CGImageDestinationFinalize image destination does not have enough images
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextTranslateCTM: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextScaleCTM: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextSetBaseCTM: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextSaveGState: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextSetInterpolationQuality: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextTranslateCTM: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextScaleCTM: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextSetFillColorWithColor: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextFillRects: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextTranslateCTM: invalid context 0x0
May 22 14:13:34 unknown assetsd[281] <Error>: CGContextScaleCTM: invalid context 0x0

code:

- (IBAction)saveImage:(id)sender {

    self.imageOverlay.alpha = 1;
    self.savedImage = [self maskImage:self.imgView withMask:self.baseImgView];

    UIImageWriteToSavedPhotosAlbum(self.savedImage, self, @selector(imageSavedToPhotosAlbum: didFinishSavingWithError: contextInfo:), nil);
}


- (UIImage*) maskImage:(UIImageView *)maskImage withMask:(UIImageView *)cropImage
{

    UIImage *image = nil;
    UIImage *imagePNG = nil;

    CGSize newImageSize = CGSizeMake(cropImage.frame.size.width, cropImage.frame.size.height);

    UIGraphicsBeginImageContextWithOptions(newImageSize, NO, 0.0); //retina res
    [self.viewForImg.layer renderInContext:UIGraphicsGetCurrentContext()];

    image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext(); 

    NSData *imgData =  UIImagePNGRepresentation ( image ); // get PNG representation
    imagePNG = [UIImage imageWithData:imgData]; // wrap UIImage around PNG representation

    return imagePNG;
}

Answer 1

This could happen if the CGSize you’re passing to UIGraphicsBeginImageContextWithOptions is CGSizeZero. I suppose the cropImage argument is either nil or its size is CGSizeZero. Please debug and make sure you have all objects initialized and with correct frames.