If you have an image view and want to crop it to a diamond (rhombus) shape, you should:
- Create
UIBezierPath
in diamond shape;
- Use that as the
path
of a CAShapeLayer
;
- Set that
CAShapeLayer
as the mask
of the UIImageView
's layer
In Swift 3 and later, that might look like:
extension UIView {
func addDiamondMask(cornerRadius: CGFloat = 0) {
let path = UIBezierPath()
path.move(to: CGPoint(x: bounds.midX, y: bounds.minY + cornerRadius))
path.addLine(to: CGPoint(x: bounds.maxX - cornerRadius, y: bounds.midY))
path.addLine(to: CGPoint(x: bounds.midX, y: bounds.maxY - cornerRadius))
path.addLine(to: CGPoint(x: bounds.minX + cornerRadius, y: bounds.midY))
path.close()
let shapeLayer = CAShapeLayer()
shapeLayer.path = path.cgPath
shapeLayer.fillColor = UIColor.white.cgColor
shapeLayer.strokeColor = UIColor.white.cgColor
shapeLayer.lineWidth = cornerRadius * 2
shapeLayer.lineJoin = kCALineJoinRound
shapeLayer.lineCap = kCALineCapRound
layer.mask = shapeLayer
}
}
So, just call addDiamondMask(cornerRadius:)
(where the cornerRadius
is optional), on your image view.
imageView.addDiamondMask()
That yields:
For Swift 2 rendition, see previous revision of this answer.
An alternate algorithm for rounding of corners might be:
extension UIView {
func addDiamondMask(cornerRadius: CGFloat = 0) {
let path = UIBezierPath()
let points = [
CGPoint(x: bounds.midX, y: bounds.minY),
CGPoint(x: bounds.maxX, y: bounds.midY),
CGPoint(x: bounds.midX, y: bounds.maxY),
CGPoint(x: bounds.minX, y: bounds.midY)
]
path.move(to: point(from: points[0], to: points[1], distance: cornerRadius, fromStart: true))
for i in 0 ..< 4 {
path.addLine(to: point(from: points[i], to: points[(i + 1) % 4], distance: cornerRadius, fromStart: false))
path.addQuadCurve(to: point(from: points[(i + 1) % 4], to: points[(i + 2) % 4], distance: cornerRadius, fromStart: true), controlPoint: points[(i + 1) % 4])
}
path.close()
let shapeLayer = CAShapeLayer()
shapeLayer.path = path.cgPath
shapeLayer.fillColor = UIColor.white.cgColor
shapeLayer.strokeColor = UIColor.clear.cgColor
layer.mask = shapeLayer
}
private func point(from point1: CGPoint, to point2: CGPoint, distance: CGFloat, fromStart: Bool) -> CGPoint {
let start: CGPoint
let end: CGPoint
if fromStart {
start = point1
end = point2
} else {
start = point2
end = point1
}
let angle = atan2(end.y - start.y, end.x - start.x)
return CGPoint(x: start.x + distance * cos(angle), y: start.y + distance * sin(angle))
}
}
Here I'm doing quad bezier in the corners, but I think the effect for rounded corners is slightly better than the above if the diamond is at all elongated.
Anyway, that yields: