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September 27, 2019 06:10
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Photoshop style gradients in Core Graphics via use of CGShader (with thanks to @jernejstrasner, see his explanation of why your gradients might not look how your designers intended http://jernejstrasner.com/2014/01/09/smooth-gradients-ios.html) ⚠️ see comments for notes
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| func SineEaseInOutLinearAverage(x: Double) -> Double { | |
| var easeInOutSine = ((cos(M_PI * x) - 1) / -2) | |
| return (easeInOutSine + x) / 2 | |
| } | |
| func ShadingFunctionCreate(startColor: NSColor, _ endColor: NSColor, _ slopeFunction: (Double) -> Double) -> (UnsafePointer<CGFloat>, UnsafeMutablePointer<CGFloat>) -> Void { | |
| return { inData, outData in | |
| let q = CGFloat(slopeFunction(Double(inData[0]))) | |
| outData[0] = startColor.redComponent + (endColor.redComponent - startColor.redComponent) * q | |
| outData[1] = startColor.greenComponent + (endColor.greenComponent - startColor.greenComponent) * q | |
| outData[2] = startColor.blueComponent + (endColor.blueComponent - startColor.blueComponent) * q | |
| outData[3] = startColor.alphaComponent + (endColor.alphaComponent - startColor.alphaComponent) * q | |
| } | |
| } | |
| func ShadingCallback(infoPointer: UnsafeMutablePointer<Void>, inData: UnsafePointer<CGFloat>, outData: UnsafeMutablePointer<CGFloat>) -> Void { | |
| var info = UnsafeMutablePointer<Gradient>(infoPointer).memory | |
| info.shadingFunction(inData, outData) | |
| } | |
| struct Gradient { | |
| let startColor : NSColor | |
| let endColor : NSColor | |
| let from : CGPoint | |
| let to : CGPoint | |
| let colorSpace = NSColorSpace.genericRGBColorSpace().CGColorSpace! | |
| init(startColor: NSColor, endColor: NSColor, from: CGPoint, to: CGPoint) { | |
| self.startColor = startColor | |
| self.endColor = endColor | |
| self.from = from | |
| self.to = to | |
| } | |
| lazy var shadingFunction : (UnsafePointer<CGFloat>, UnsafeMutablePointer<CGFloat>) -> Void = { | |
| return ShadingFunctionCreate(self.startColor, self.endColor, SineEaseInOutLinearAverage) | |
| }() | |
| lazy var CGFunction : CGFunctionRef? = { | |
| var callbacks = CGFunctionCallbacks(version: 0, evaluate: ShadingCallback, releaseInfo: nil) | |
| return CGFunctionCreate(&self, 1, [0, 1], 4, [0, 1, 0, 1, 0, 1, 0, 1], &callbacks) | |
| }() | |
| lazy var CGShading : CGShadingRef! = CGShadingCreateAxial(self.colorSpace, self.from, self.to, self.CGFunction, false, false) | |
| } |
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Hi, I have an update for Swift 5 on iOS.
https://gist.github.com/LiLejia/3b67b5d3e0a83eb3ef251533e52a0889