Save CIImage, by converting to CGImage, throws an error

Question

I have an image I'm grabbing from AVFoundation:

[stillImage captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageSampleBuffer, NSError *error) {
    NSLog(@"image capture");

    NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
    UIImage *image = [[UIImage alloc] initWithData:imageData];

I'm then cropping this image by first converting to a CIImage:

beginImage = [CIImage imageWithCVPixelBuffer:CMSampleBufferGetImageBuffer(imageSampleBuffer) options:[NSDictionary dictionaryWithObjectsAndKeys:[NSNull null], kCIImageColorSpace, nil]];

    //first we crop to a square
    crop = [CIFilter filterWithName:@"CICrop"];
    [crop setValue:[CIVector vectorWithX:0 Y:0 Z:70 W:70] forKey:@"inputRectangle"];
    [crop setValue:beginImage forKey:@"inputImage"];
    croppedColourImage = [crop valueForKey:@"outputImage"];

I'm then trying to convert this back to a CGImage so that I can save it out:

CGImageRef cropColourImage = [context createCGImage:croppedColourImage fromRect:[croppedColourImage extent]];
    UIImage *cropSaveImage = [UIImage imageWithCGImage:cropColourImage];


    //saving of the images
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

     [library writeImageToSavedPhotosAlbum:[cropSaveImage CGImage] orientation:(ALAssetOrientation)[image imageOrientation] completionBlock:^(NSURL *assetURL, NSError *error){
     if (error) {
         NSLog(@"ERROR in image save :%@", error);
     } else
     {
         NSLog(@"SUCCESS in image save");
     }

     }];

However, this throws the error:

ERROR in image save :Error Domain=ALAssetsLibraryErrorDomain Code=-3304 "Failed to encode image for saved photos." UserInfo=0x19fbd0 {NSUnderlyingError=0x18efa0 "Failed to encode image for saved photos.", NSLocalizedDescription=Failed to encode image for saved photos.}

I've read elsewhere that this can happen if the image was 0x0 pixels, and that the conversion from CIImage to CGImage can cause the problem. Any ideas?

Thank you.

I Believe this is because the image I'm trying to save has no dimensions, width and height appear to be null. "2012-05-06 14:39:22.886 zApp[5108:707] Image being saved has width of: (null) 2012-05-06 14:39:22.890 zApp[5108:707] Image being saved has height of: (null)" — mrEmpty
I had an error in my NSLog code, I can confirm the image I'm trying to save is 0x0 pixels. So that I think is the problem, but I can't see what that would be happening. — mrEmpty

mrEmpty mrEmpty · Accepted Answer · 2012-05-06T17:59:58

I got it working!

What I did is replace all my code with:

NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
UIImage *image = [[UIImage alloc] initWithData:imageData];
NSLog(@"*image size is: %@", NSStringFromCGSize(image.size));

//test creating a new ciimage
CIImage *ciImage = [[CIImage alloc] initWithCGImage:[image CGImage]];
NSLog(@"ciImage extent: %@", NSStringFromCGRect([ciImage extent]));

This gives me a usable CIImage. I can then have filter fun with it, before saving it with:

CIImage *croppedColourImage = [crop outputImage];

//convert it to a cgimage for saving
CGImageRef cropColourImage = [context createCGImage:croppedColourImage fromRect:[croppedColourImage extent]];

//saving of the images
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

[library writeImageToSavedPhotosAlbum:cropColourImage metadata:[croppedColourImage properties] completionBlock:^(NSURL *assetURL, NSError *error){
    if (error) {
        NSLog(@"ERROR in image save: %@", error);
    } else
    {
        NSLog(@"SUCCESS in image save");
        CGImageRelease(cropColourImage);
    }
}];

Save CIImage, by converting to CGImage, throws an error

1 Answers