CIDetector Perspective And Crop in Swift

Question

I've implemented a CIDetector in my app to detect rectangles on a image, but now how can i use the returned CGPoint's to crop the image so that i can display it back?

For the perspective i've tried applying the CIPerspectiveCorrection filter, but couldn't get it to work.

I've searched around and found some clues but couldn't find a solution in Swift.

How do i use the data provided by the CIDetector (detected rectangle) to fix perspective and crop my image?

For anyone who might not be familiar with what a CIDetectorTypeRectangle returns: it returns 4 CGPoint's bottomLeft,bottomRight,topLeft,topRight.

Answer 1

Here's what worked:

func flattenImage(image: CIImage, topLeft: CGPoint, topRight: CGPoint,bottomLeft: CGPoint, bottomRight: CGPoint) -> CIImage {

    return image.applyingFilter("CIPerspectiveCorrection", withInputParameters: [

        "inputTopLeft": CIVector(cgPoint: topLeft),
        "inputTopRight": CIVector(cgPoint: topRight),
        "inputBottomLeft": CIVector(cgPoint: bottomLeft),
        "inputBottomRight": CIVector(cgPoint: bottomRight)


        ])

}

Wherever you detect your rectangle:

UIGraphicsBeginImageContext(CGSize(width: flattenedImage!.extent.size.height, height: flattenedImage!.extent.size.width))

UIImage(ciImage:resultImage!,scale:1.0,orientation:.right).draw(in: CGRect(x: 0, y: 0, width: resultImage!.extent.size.height, height: resultImage!.extent.size.width))

let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()