iOS 7 Core Image QR Code generation too blur

Easiest solution is to add following to your image view:

imgViewQR.layer.magnificationFilter = kCAFilterNearest

This will automatically upscale your generated QR code image to imageview's size using nearest which results in sharp, pixelated image. This usually isn't what you want when resizing icons/photos but is perfect for QR codes

(it doesn't seem to work on simulator but works great on real device)

I was about to start bounty on this question but i found the answer.

What you need is a scale filter. To achieve this with CoreImage, you need to do something like this:

CIImage *input = [CIImage imageWithCGImage: ImageView.Image.CGImage]; // input image is 100 X 100
CGAffineTransform transform = CGAffineTransformMakeScale(5.0f, 5.0f); // Scale by 5 times along both dimensions
CIImage *output = [input imageByApplyingTransform: transform];
// output image is now 500 X 500

FROM THIS SO ANSWER: https://stackoverflow.com/a/16316701/2859764

This method will use CoreImage to generate the QR code as a CIImage. Unfortunately, there's no simple way to disable interpolation, so scaling the image will create a blurry code. The workaround is to create temporary CGImageRef with the bits and draw it into a grayscale bitmap CGContextRef.

Tested on OSX but should work on iOS as written.

- (CGImageRef)createQRImageForString:(NSString *)string size:(CGSize)size {
  // Setup the QR filter with our string
  CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
  [filter setDefaults];

  NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
  [filter setValue:data forKey:@"inputMessage"];
  CIImage *image = [filter valueForKey:@"outputImage"];

  // Calculate the size of the generated image and the scale for the desired image size
  CGRect extent = CGRectIntegral(image.extent);
  CGFloat scale = MIN(size.width / CGRectGetWidth(extent), size.height / CGRectGetHeight(extent));

  // Since CoreImage nicely interpolates, we need to create a bitmap image that we'll draw into
  // a bitmap context at the desired size;
  size_t width = CGRectGetWidth(extent) * scale;
  size_t height = CGRectGetHeight(extent) * scale;
  CGColorSpaceRef cs = CGColorSpaceCreateDeviceGray();
  CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, cs, (CGBitmapInfo)kCGImageAlphaNone);

#if TARGET_OS_IPHONE
  CIContext *context = [CIContext contextWithOptions:nil];
#else
  CIContext *context = [CIContext contextWithCGContext:bitmapRef options:nil];
#endif

  CGImageRef bitmapImage = [context createCGImage:image fromRect:extent];

  CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationNone);
  CGContextScaleCTM(bitmapRef, scale, scale);
  CGContextDrawImage(bitmapRef, extent, bitmapImage);

  // Create an image with the contents of our bitmap
  CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);

  // Cleanup
  CGContextRelease(bitmapRef);
  CGImageRelease(bitmapImage);

  return scaledImage;
}