我怎样才能调整CIImage的大小

Question

  

可能重复：
  resizing a UIImage without loading it entirely into memory?

我如何调整CIImage的大小？

NSDictionary *imageOptions = nil;
NSNumber *orientation = CMGetAttachment(imageDataSampleBuffer, kCGImagePropertyOrientation, NULL);
if (orientation) {
    imageOptions = [NSDictionary dictionaryWithObject:orientation forKey:CIDetectorImageOrientation];
}

NSArray *features = [faceDetector featuresInImage:ciImage options:imageOptions];

我需要在ciImage中设置要素的宽度。