The technically accurate answer is that a CIFilter requires a CIImage. You can turn a UIView into a UIImage and then convert that into a CIImage, but all CoreImage filters that use an image for input (there are some that generate a new image) use a `CIImage for input and output.
- Please note that the origin for a
CIImage is bottom left, not top left. Basically the Y axis is flipped.
- If you use CoreImage filters dynamically, learn to use a
GLKView to render in - it uses the GPU where a UIImageView uses the CPU.
- If you want to test out a filter, it's best to use an actual device. The simulator will give you very poor performance. I've seen a simple blur take nearly a minute where on a device it will be a fraction of a second!
Let's say you have a UIView that you wish to apply a CIPhotoEffectMono to. The steps to do this would be:
- Convert the
UIView into a CIImage.
- Apply the filter, getting a
CIImage as output.
- Use a
CIContext to create a CGImage and then convert that to a UIImage.
Here's a UIView extension that will convert the view and all it's subviews into a UIImage:
extension UIView {
public func createImage() -> UIImage {
UIGraphicsBeginImageContextWithOptions(
CGSize(width: self.frame.width, height: self.frame.height), true, 1)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image!
}
}
Converting a UIImage into a CIImage is one line of code:
let ciInput = CIImage(image: myView.createImage)
Here's a function that will apply the filter and return a UIImage:
func convertImageToBW(image:UIImage) -> UIImage {
let filter = CIFilter(name: "CIPhotoEffectMono")
// convert UIImage to CIImage and set as input
let ciInput = CIImage(image: image)
filter?.setValue(ciInput, forKey: "inputImage")
// get output CIImage, render as CGImage first to retain proper UIImage scale
let ciOutput = filter?.outputImage
let ciContext = CIContext()
let cgImage = ciContext.createCGImage(ciOutput!, from: (ciOutput?.extent)!)
return UIImage(cgImage: cgImage!)
}
