Getting a CGImage from CIImage

Question

I have a UIImage which is loaded from a CIImage with:

tempImage = [UIImage imageWithCIImage:ciImage];

The problem is I need to crop tempImage to a specific CGRect and the only way I know how to do this is by using CGImage. The problem is that in the iOS 6.0 documentation I found this:

CGImage
If the UIImage object was initialized using a CIImage object, the value of the property is NULL.

A. How to convert from CIImage to CGImage? I'm using this code but I have a memory leak (and can't understand where):

+(UIImage*)UIImageFromCIImage:(CIImage*)ciImage {       CGSize size = ciImage.extent.size;       UIGraphicsBeginImageContext(size);       CGRect rect;       rect.origin = CGPointZero;       rect.size   = size;       UIImage *remImage = [UIImage imageWithCIImage:ciImage];       [remImage drawInRect:rect];       UIImage *result = UIGraphicsGetImageFromCurrentImageContext();       UIGraphicsEndImageContext();       remImage = nil;       ciImage = nil;       //     return result;   } 

Answer 1

Swift 3, Swift 4 and Swift 5

Here is a nice little function to convert a CIImage to CGImage in Swift.

func convertCIImageToCGImage(inputImage: CIImage) -> CGImage? {     let context = CIContext(options: nil)     if let cgImage = context.createCGImage(inputImage, from: inputImage.extent) {         return cgImage     }     return nil } 

Notes:

• CIContext(options: nil) will use a software renderer and can be quite slow. To improve the performance, use CIContext(options: [CIContextOption.useSoftwareRenderer: false]) - this forces operations to run on GPU, and can be much faster.
• If you use CIContext more than once, cache it as apple recommends.

Answer 2

See the CIContext documentation for createCGImage:fromRect:

CGImageRef img = [myContext createCGImage:ciImage fromRect:[ciImage extent]]; 

From an answer to a similar question: https://stackoverflow.com/a/10472842/474896

Also since you have a CIImage to begin with, you could use CIFilter to actually crop your image.