从CMSampleBuffer捕获UIImage（swift 3）

Question

I try to capture an UIImage from a CMSampleBuffer to read the text. But I always get the error:

fatal error: unexpectedly found nil while unwrapping an Optional value

I was looking around and tried a lot of versions. But I always get the same error.

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {

        let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
        let image = CIImage(cvPixelBuffer: pixelBuffer!)
            let uiImage = UIImage(cgImage: image.cgImage!)
}

kindly Regards!

Answer 1

CIImage.cgImage applies only when the CIImage was created from a CGImage . When you create a CIImage from a pixel buffer, it has no underlying CGImage so that property is nil.

You can initialize a UIImage direct from a CIImage , but how that works for you will depend on where/how you render that image. (For example rendering CI-backed UIImage s in, say, UIImageView gives poor performance in iOS 9 and older if you're doing it in realtime.)

Answer 2

To get the UIImage via CIImage you should use CIContext. Below is Obj-C code:

CIContext *context = [CIContext contextWithOptions:nil];

And then:

CGImageRef cgImage = [context createCGImage:yourCIImage fromRect:[yourCIImage extent] ];
UIImage *resultUIImage = [UIImage imageWithCGImage:cgImage scale:1.0 orientation:UIImageOrientationUp];

This approach claims it only uses GPU and thus is fast. But there are other methods to obtain UIImage from the CVPixelBuffer , like using CGContextRef .