Caps-iOS/Caps/Extensions/UIImage+Extensions.swift

import Foundation
import UIKit


extension UIImage {

    static func templateImage(named: String) -> UIImage {
        return UIImage(named: named)!.withRenderingMode(.alwaysTemplate)
    }

    /**
     Resize an image to the target size
     */
    func resize(to targetSize: CGSize) -> UIImage {
        let rect = CGRect(x: 0, y: 0, width: targetSize.width, height: targetSize.height)

        UIGraphicsBeginImageContextWithOptions(targetSize, false, scale)
        self.draw(in: rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage!
    }

    /**
     Crop an image to a square, centered around the middle of the frame
     - parameter factor: The crop factor of the resulting image
     - returns: The cropped image
     */
    func crop(factor: CGFloat) -> UIImage {
        let width = size.width * scale * factor
        return crop(to: width)
    }

    /**
     Crop an image to a square, centered around the middle of the frame
     - parameter size: The height and width of the resulting image
     - returns: The cropped image
     */
    func crop(to size: CGFloat) -> UIImage {
        let rect = CGRect(
            x: (self.size.height * scale - size) / 2,
            y: (self.size.width * scale - size) / 2,
            width: size * scale,
            height: size * scale)

        let imageRef = cgImage!.cropping(to: rect)
        return UIImage(cgImage: imageRef!, scale: scale, orientation: imageOrientation)
    }

    /// The (circular) image masked by a circle
    var circleMasked: UIImage? {
        let width = size.width
        let height = size.height
        let isPortrait = height > width
        let breadth = min(width, height)
        let breadthSize = CGSize(width: breadth, height: breadth)
        let breadthRect = CGRect(origin: .zero, size: breadthSize)
        UIGraphicsBeginImageContextWithOptions(breadthSize, false, scale)
        defer { UIGraphicsEndImageContext() }

        let x = isPortrait ? 0 : floor((width - height) / 2)
        let y = isPortrait ? floor((height - width) / 2) : 0
        let rect = CGRect(origin: CGPoint( x: x, y: y), size: breadthSize)
        guard let cgImage = cgImage?.cropping(to: rect) else {
            return nil
        }
        UIBezierPath(ovalIn: breadthRect).addClip()
        UIImage(cgImage: cgImage, scale: scale, orientation: imageOrientation).draw(in: breadthRect)
        return UIGraphicsGetImageFromCurrentImageContext()
    }

    var averageColor: UIColor? {
        let image = ciImage ?? CIImage(cgImage: cgImage!)
        return image.averageColor
    }
}

extension CIImage {

    func averageColor(context: CIContext) -> UIColor? {
        let extentVector = CIVector(
            x: extent.origin.x,
            y: extent.origin.y,
            z: extent.size.width,
            w: extent.size.height)

        guard let filter = CIFilter(name: "CIAreaAverage", parameters: [kCIInputImageKey: self, kCIInputExtentKey: extentVector]) else {
            log("Failed to create filter")
            return nil
        }
        guard let outputImage = filter.outputImage else {
            log("Failed get filter output")
            return nil
        }

        var bitmap = [UInt8](repeating: 0, count: 4)

        context.render(outputImage, toBitmap: &bitmap, rowBytes: 4,
                       bounds: CGRect(x: 0, y: 0, width: 1, height: 1),
                       format: .RGBA8, colorSpace: nil)

        return UIColor(
            red: saturate(bitmap[0]),
            green: saturate(bitmap[1]),
            blue: saturate(bitmap[2]),
            alpha: CGFloat(bitmap[3]) / 255)
    }

    var averageColor: UIColor? {
        let extentVector = CIVector(
            x: extent.origin.x,
            y: extent.origin.y,
            z: extent.size.width,
            w: extent.size.height)

        guard let filter = CIFilter(name: "CIAreaAverage", parameters: [kCIInputImageKey: self, kCIInputExtentKey: extentVector]) else {
            log("Failed to create filter")
            return nil
        }
        guard let outputImage = filter.outputImage else {
            log("Failed get filter output")
            return nil
        }

        var bitmap = [UInt8](repeating: 0, count: 4)
        guard let null = kCFNull else {
            return nil
        }
        let context = CIContext(options: [.workingColorSpace: null])
        context.render(outputImage, toBitmap: &bitmap, rowBytes: 4,
                       bounds: CGRect(x: 0, y: 0, width: 1, height: 1),
                       format: .RGBA8, colorSpace: nil)

        let color = UIColor(
            red: saturate(bitmap[0]),
            green: saturate(bitmap[1]),
            blue: saturate(bitmap[2]),
            alpha: CGFloat(bitmap[3]) / 255)

        return color
    }
}

/// Map expected range 75-200 to 0-255
private func saturate(_ component: UInt8) -> CGFloat {
    return max(min(CGFloat(component) * 2 - 150, 255), 0) / 255
}

extension CIImage: Logger { }


extension UIImage {

    convenience init?(at url: URL) {
        guard let data = try? Data(contentsOf: url) else {
            return nil
        }
        self.init(data: data, scale: UIScreen.main.scale)
    }
}