Zxing zoom functionality in ios AVFoundation

Question

I have been scouring the internet and have been looking high and low for any type of code to help me zoom in on barcodes using ZXing.

I started with the code from their git site here

https://github.com/zxing/zxing

Since then I have been able to increase the default resolution to 1920x1080.

self.captureSession.sessionPreset = AVCaptureSessionPreset1920x1080;

This would be fine but the issue is that I am scanning very small barcodes and even though 1920x1080 would work it doesnt give me any kind of zoom to capture closer to a smaller barcode without losing focus. Now the resolution did help me quite a bit but its simply not close enough.

Im thinking what I need to do is to set the capture session to a scroll view that is 1920x1080 and then set the actual image capture to take from the bounds of my screen so i can zoom in and out of the scroll view itself to achieve a "zoom" kind of affect.

The problem with that is im really not sure where to start...any ideas?

Answer 1

Ok since I have seen this multiple time on here and no one seems to have an answer. I thought I would share my own answer.

There are 2 properties NO ONE seems to know about. Ill cover both.

Now the first one is good for iOS 6+. Apple added a property called setVideoScaleAndCropfactor.

This setting this returns a this is a CGFloat type. The only downfall in this is that you have to set the value to your AVConnection and then set the connection to a stillImageCapture. It will not work with anything else in iOS 6. Now in order to do this you have to set it up to work Asynchronously and you have to loop your code for the decoder to work and take pictures at that scale.

Last thing is that you have to scale your preview layer yourself.

This all sounds like a lot of work. And it really really is. However, This sets your original scan picture to be taken at 1920x1080 or whatever you have it set as. Rather than scaling a current image which will stretch pixels causing the decoder to miss the barcode.

Sp this will look something like this

stillImageConnection = [stillImageOutput connectionWithMediaType:AVMediaTypeVideo];
[stillImageConnection setVideoOrientation:AVCaptureVideoOrientationPortrait];
[stillImageConnection setVideoScaleAndCropFactor:effectiveScale];
[stillImageOutput setOutputSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCMPixelFormat_32BGRA]
                                                                forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
[stillImageOutput captureStillImageAsynchronouslyFromConnection:stillImageConnection
                                              completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error)
 {
     if(error)
         return;
     NSString *path = [NSString stringWithFormat:@"%@%@",
                       [[NSBundle mainBundle] resourcePath],
                       @"/blank.wav"];
     SystemSoundID soundID;
     NSURL *filePath = [NSURL fileURLWithPath:path isDirectory:NO];
     AudioServicesCreateSystemSoundID(( CFURLRef)filePath, &soundID);
     AudioServicesPlaySystemSound(soundID);
     CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(imageDataSampleBuffer);
     /*Lock the image buffer*/
     CVPixelBufferLockBaseAddress(imageBuffer,0);
     /*Get information about the image*/
     size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
     size_t width = CVPixelBufferGetWidth(imageBuffer);
     size_t height = CVPixelBufferGetHeight(imageBuffer);

     uint8_t* baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);
     void* free_me = 0;
     if (true) { // iOS bug?
         uint8_t* tmp = baseAddress;
         int bytes = bytesPerRow*height;
         free_me = baseAddress = (uint8_t*)malloc(bytes);
         baseAddress[0] = 0xdb;
         memcpy(baseAddress,tmp,bytes);
     }

     CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
     CGContextRef newContext =
     CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace,
                           kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipFirst);

     CGImageRef capture = CGBitmapContextCreateImage(newContext);
     CVPixelBufferUnlockBaseAddress(imageBuffer,0);
     free(free_me);

     CGContextRelease(newContext);
     CGColorSpaceRelease(colorSpace);

     Decoder* d = [[Decoder alloc] init];
     [self decoding:d withimage:&capture];
 }];

}

Now the second one that is coming in iOS 7 that will change EVERYTHING I just said. You have a new property called videoZoomFactor. this is a CGFloat. However it changes everything at the TOP of the stack rather than just affecting like the stillimagecapture.

In Otherwords you wont have to manually zoom your preview layer. You wont have to go through some stillimagecaptureloop and you wont have to set it to an AVConnection. You simply set the CGFloat and it scales everything for you.

Now I know its going to be a while before you can publish iOS 7 applications. So I would seriously consider figuring out how to do this the hard way. Quick tips. I would use a pinch and zoom gesture to set your CGFloat for setvideoscaleandcropfactor. Dont forget to set the value to 1 in your didload and you can scale from there. At the same time in your gesture you can use it to do your CATransaction to scale the preview layer.

Heres a sample of how to do the gesture capture and preview layer

    - (IBAction)handlePinchGesture:(UIPinchGestureRecognizer *)recognizer
    {
effectiveScale = recognizer.scale;
if (effectiveScale < 1.0)
    effectiveScale = 1.0;
if (effectiveScale > 25)
    effectiveScale = 25;

stillImageConnection = [stillImageOutput connectionWithMediaType:AVMediaTypeVideo];
[stillImageConnection setVideoScaleAndCropFactor:effectiveScale];

[CATransaction begin];
[CATransaction setAnimationDuration:0];
[prevLayer setAffineTransform:CGAffineTransformMakeScale(effectiveScale, effectiveScale)];
[CATransaction commit];

}

Hope this helps someone out! I may go ahead and just to a video tutorial on this. Depends on what kind of demand there is for it I guess.