Swift extension for UIImageView that allows to draw contrast label upon image content
Download UIImageViewContrastLabel.swift and threshold.cikernel from UIImageViewContrastLabel folder, add them to your project.
Change let bundle = Bundle(identifier: "bivanov.UIImageViewContrastLabel")! to whatever bundle you're using in UIImageViewContrastLabel.swift
Add github "bivanov/UIImageViewContrastLabel" to your Cartfile
Releases before 1.0.5 support Swift3. Release 1.0.5 supports Swift4. All releases from 1.0.6 support Swift5.
class ViewController: UIViewController {
@IBOutlet weak var imageView: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
imageView.addContrastLabel(text: "Hello world!", font: UIFont(name: "Courier", size: 15.0)!)
}
// ...
}
If you want to place label not in left upper corner of image view, you may specify relative position with coordinates in range from 0 to 1:
let text = "Hello world!"
let font = UIFont(name: "Courier", size: 15.0)!
let position = CGPoint(x: 0.2, y: 0.5)
imageView.addContrastLabel(text: text, font: font, position: position)
You can specify colors that will be used for "light" and "dark" parts of contrast label:
let darkPartsColor =
CIColor(red: 137.0 / 255.0, green: 32.0 / 255.0, blue: 29.0 / 255.0)
let lightPartsColor =
CIColor(red: 19.0 / 255.0, green: 44.0 / 255.0, blue: 85.0 / 255.0)
let position = CGPoint(x: 0.5, y: 0.5)
self.constrastLayer = imageView.addContrastLabel(text: "Hello world!",
font: UIFont(name: "Helvetica", size: 45.0)!,
position: position,
darkPartsColor: darkPartsColor,
lightPartsColor: lightPartsColor)
By default, these colors are white and black correspondingly.
To remove contrast label from UIImageView, just call
imageView.removeContrastLabel()
CAContrastLabelLayer that is being used under the hood is not directly animatable, but you can animate underlying text layer:
class ViewController: UIViewController {
@IBOutlet weak var imageView: UIImageView!
var constrastLayer: CAContrastLabelLayer!
override func viewDidLoad() {
super.viewDidLoad()
self.constrastLayer = imageView.addContrastLabel(text: "Hello world!",
font: UIFont(name: "Courier", size: 15.0)!)
DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) { [unowned self] in
self.animateContrastLabel()
}
}
// ...
func animateContrastLabel() {
let animation = CABasicAnimation(keyPath: #keyPath(CATextLayer.position))
animation.duration = 4.0
animation.repeatCount = 1.0
animation.fromValue = self.constrastLayer.textLayer.position
animation.toValue = CGPoint(x: self.constrastLayer.textLayer.position.x,
y: 300)
self.constrastLayer.textLayer.add(animation, forKey: "position")
}
}
CAContrastLabelLayer has textPosition property to control relative position of text, but this property is not animatable as well.
Demo image by Katie Walker
MIT license