iOS 使用 CIFilter 缩放/扭曲图像的特定部分

Question

The use case is to detect something in an image and zoom\/distort-outward it as in you are looking through a magnifying glass.

let distortion = CIFilter(name: "CIHoleDistortion")
distortion.setValue(sourceImage, forKey: kCIInputImageKey)
distortion.setValue(CIVector.init(cgPoint: CGPoint.init(x: 200, y: 200)), forKey: "inputCenter")
distortion.setValue(NSNumber.init(value: 100), forKey: "inputRadius")

Answer 1

CIBumpDistortion怎么CIBumpDistortion ？

Answer 2

CIBumpDistortion as mentioned by Frank above, but the scale parameter actually works as follows: scale < 0 -> concave; scale > 0 -> convex.

Answer 3

Another (and maybe better) option is to use CIGlassLozenge filter:

1. Set inputRefraction to something slightly larger than 1 (eg 1.06)
2. Allign both inputPoint0 and inputPoint1 with the coordinate of the zoom point
3. Play with the radius to get the desired effect. The attached example uses radius 1000.

If you want to play with this filter (and any other out of 250 CIFilters) in real time check this app out: https://apps.apple.com/us/app/filter-magic/id1594986951