SKTexture gradient

SpriteKit at times can seem a little rudimentary – small tasks can seem to take longer than they should! Today I ran into a limitation of SKShapeNodes – there doesn’t seem to be a default way to set up a gradient fill. I have created an extension to SKTexture to generate a gradient – you can then use this SKTexture in a SKShapeNode (fillTexture) or a SKSpriteNode.

Credit to an Objective C class developed by Joseph Preiss that I found here and heavily based my Swift version on. I made it an extension of SKTexture and added gradient direction.

[sourcecode language=”javascript”]
enum GradientDirection {
case up
case left
case upLeft
case upRight
}
extension SKTexture {
convenience init(size:CGSize,color1:CIColor,color2:CIColor,direction:GradientDirection = .up) {
let coreImageContext = CIContext(options: nil)
let gradientFilter = CIFilter(name: "CILinearGradient")
gradientFilter.setDefaults()
var startVector:CIVector
var endVector:CIVector
switch direction {
case .up:
startVector = CIVector(x: size.width/2, y: 0)
endVector = CIVector(x: size.width/2, y: size.height)
case .left:
startVector = CIVector(x: size.width, y: size.height/2)
endVector = CIVector(x: 0, y: size.height/2)
case .upLeft:
startVector = CIVector(x: size.width, y: 0)
endVector = CIVector(x: 0, y: size.height)
case .upRight:
startVector = CIVector(x: 0, y: 0)
endVector = CIVector(x: size.width, y: size.height)

}
gradientFilter.setValue(startVector, forKey: "inputPoint0")
gradientFilter.setValue(endVector, forKey: "inputPoint1")
gradientFilter.setValue(color1, forKey: "inputColor0")
gradientFilter.setValue(color2, forKey: "inputColor1")
let cgimg = coreImageContext.createCGImage(gradientFilter.outputImage, fromRect: CGRect(x: 0, y: 0, width: size.width, height: size.height))
self.init(CGImage:cgimg)
}
}
[/sourcecode]

About craiggrummitt

iOS development with Swift - book: https://manning.com/books/ios-development-with-swift video course: https://www.manning.com/livevideo/ios-development-with-swift-lv