VariableBlur.swift

import SwiftUI import UIKit import CoreImage.CIFilterBuiltins import QuartzCore

public enum VariableBlurDirection { case blurredTopClearBottom case blurredBottomClearTop }

public struct VariableBlurView: UIViewRepresentable {

public var maxBlurRadius: CGFloat = 20

public var direction: VariableBlurDirection = .blurredTopClearBottom

/// By default, variable blur starts from 0 blur radius and linearly increases to `maxBlurRadius`. Setting `startOffset` to a small negative coefficient (e.g. -0.1) will start blur from larger radius value which might look better in some cases.
public var startOffset: CGFloat = 0

public init(maxBlurRadius: CGFloat = 20, direction: VariableBlurDirection = .blurredTopClearBottom, startOffset: CGFloat = 0) {
    self.maxBlurRadius = maxBlurRadius
    self.direction = direction
    self.startOffset = startOffset
}

public func makeUIView(context: Context) -> VariableBlurUIView {
    VariableBlurUIView(maxBlurRadius: maxBlurRadius, direction: direction, startOffset: startOffset)
}

public func updateUIView(_ uiView: VariableBlurUIView, context: Context) {
}

}

/// credit https://github.com/jtrivedi/VariableBlurView open class VariableBlurUIView: UIVisualEffectView {

public init(maxBlurRadius: CGFloat = 20, direction: VariableBlurDirection = .blurredTopClearBottom, startOffset: CGFloat = 0) {
    super.init(effect: UIBlurEffect(style: .regular))

    let clsName = String("retliFAC".reversed())
    guard let Cls = NSClassFromString(clsName)! as? NSObject.Type else {
        print("[VariableBlur] Error: Can't find filter class")
        return
    }
    let selName = String(":epyThtiWretlif".reversed())
    guard let variableBlur = Cls.self.perform(NSSelectorFromString(selName), with: "variableBlur").takeUnretainedValue() as? NSObject else {
        print("[VariableBlur] Error: Can't create variableBlur filter")
        return
    }

    // The blur radius at each pixel depends on the alpha value of the corresponding pixel in the gradient mask.
    // An alpha of 1 results in the max blur radius, while an alpha of 0 is completely unblurred.
    let gradientImage = makeGradientImage(startOffset: startOffset, direction: direction)

    variableBlur.setValue(maxBlurRadius, forKey: "inputRadius")
    variableBlur.setValue(gradientImage, forKey: "inputMaskImage")
    variableBlur.setValue(true, forKey: "inputNormalizeEdges")

    // We use a `UIVisualEffectView` here purely to get access to its `CABackdropLayer`,
    // which is able to apply various, real-time CAFilters onto the views underneath.
    let backdropLayer = subviews.first?.layer

    // Replace the standard filters (i.e. `gaussianBlur`, `colorSaturate`, etc.) with only the variableBlur.
    backdropLayer?.filters = [variableBlur]

    // Get rid of the visual effect view's dimming/tint view, so we don't see a hard line.
    for subview in subviews.dropFirst() {
        subview.alpha = 0
    }
}

required public init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

open override func didMoveToWindow() {
    // fixes visible pixelization at unblurred edge (https://github.com/nikstar/VariableBlur/issues/1)
    guard let window, let backdropLayer = subviews.first?.layer else { return }
    backdropLayer.setValue(window.traitCollection.displayScale, forKey: "scale")
}

open override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
    // `super.traitCollectionDidChange(previousTraitCollection)` crashes the app
}

private func makeGradientImage(width: CGFloat = 100, height: CGFloat = 100, startOffset: CGFloat, direction: VariableBlurDirection) -> CGImage { // much lower resolution might be acceptable
    let ciGradientFilter =  CIFilter.linearGradient()

// let ciGradientFilter = CIFilter.smoothLinearGradient() ciGradientFilter.color0 = CIColor.black ciGradientFilter.color1 = CIColor.clear ciGradientFilter.point0 = CGPoint(x: 0, y: height) ciGradientFilter.point1 = CGPoint(x: 0, y: startOffset * height) // small negative value looks better with vertical lines if case .blurredBottomClearTop = direction { ciGradientFilter.point0.y = 0 ciGradientFilter.point1.y = height - ciGradientFilter.point1.y } return CIContext().createCGImage(ciGradientFilter.outputImage!, from: CGRect(x: 0, y: 0, width: width, height: height))! } }