I'm trying to clip a UIImage
based on a given UIBezierPath
, but the resulting image retains the original shape and size. I want the shape and size to resemble the path, i.e. the visible content of the new image.
Take a look at this following example:
The following is the code I am using to mask an image given a path:
func imageByApplyingClippingBezierPath(_ path: UIBezierPath) -> UIImage {
UIGraphicsBeginImageContextWithOptions(CGSize(
width: size.width,
height: size.height
), false, 0.0)
let context = UIGraphicsGetCurrentContext()!
context.saveGState()
path.addClip()
draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
let newImage = UIGraphicsGetImageFromCurrentImageContext()!
context.restoreGState()
UIGraphicsEndImageContext()
return newImage
}
One solution would be to crop the image after masking it, but ideally I want this to be done as simple and efficiently as possible in one go.
Any solution/ tips would be appreciated.
Thanks to Rob I was able to implement a solution using the cropping(to:)
method of CGImage
.
This is a two step process where first I mask the image using the given path, and then crop the result using the bounds of the path.
The following is my final working source code for implementing a clipping UIBezierPath
UIImage
extension:
extension UIImage {
func imageByApplyingClippingBezierPath(_ path: UIBezierPath) -> UIImage {
// Mask image using path
let maskedImage = imageByApplyingMaskingBezierPath(path)
// Crop image to frame of path
let croppedImage = UIImage(cgImage: maskedImage.cgImage!.cropping(to: path.bounds)!)
return croppedImage
}
func imageByApplyingMaskingBezierPath(_ path: UIBezierPath) -> UIImage {
// Define graphic context (canvas) to paint on
UIGraphicsBeginImageContext(size)
let context = UIGraphicsGetCurrentContext()!
context.saveGState()
// Set the clipping mask
path.addClip()
draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
let maskedImage = UIGraphicsGetImageFromCurrentImageContext()!
// Restore previous drawing context
context.restoreGState()
UIGraphicsEndImageContext()
return maskedImage
}
}
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