[Swift]扩展UIImage :获取图片指定像素的颜色值

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对【UIImage】进行扩展

import UIKit
 
extension UIImage{
     
    /**
     根据坐标获取图片中的像素颜色值
     */
    subscript (x: Int, y: Int) -> UIColor? {
         
        if x < 0 || x > Int(size.width) || y < 0 || y > Int(size.height) {
            return nil
        }
         
        let provider = self.cgImage!.dataProvider
        let providerData = provider!.data
        let data = CFDataGetBytePtr(providerData)
         
        let numberOfComponents = 4
        let pixelData = ((Int(size.width) * y) + x) * numberOfComponents
         
        let r = CGFloat(data![pixelData]) / 255.0
        let g = CGFloat(data![pixelData + 1]) / 255.0
        let b = CGFloat(data![pixelData + 2]) / 255.0
        let a = CGFloat(data![pixelData + 3]) / 255.0
         
        return UIColor(red: r, green: g, blue: b, alpha: a)
    }
}

对【UIColor】进行扩展

import UIKit
 
extension UIColor {
     
    // Hex String -> UIColor
    convenience init(hexString: String) {
        let hexString = hexString.trimmingCharacters(in: .whitespacesAndNewlines)
        let scanner = Scanner(string: hexString)
         
        if hexString.hasPrefix("#") {
            scanner.scanLocation = 1
        }
         
        var color: UInt32 = 0
        scanner.scanHexInt32(&color)
         
        let mask = 0x000000FF
        let r = Int(color >> 16) & mask
        let g = Int(color >> 8) & mask
        let b = Int(color) & mask
         
        let red   = CGFloat(r) / 255.0
        let green = CGFloat(g) / 255.0
        let blue  = CGFloat(b) / 255.0
         
        self.init(red: red, green: green, blue: blue, alpha: 1)
    }
     
    // UIColor -> Hex String
    var hexString: String? {
        var red: CGFloat = 0
        var green: CGFloat = 0
        var blue: CGFloat = 0
        var alpha: CGFloat = 0
         
        let multiplier = CGFloat(255.999999)
         
        guard self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) else {
            return nil
        }
         
        if alpha == 1.0 {
            return String(
                format: "#%02lX%02lX%02lX",
                Int(red * multiplier),
                Int(green * multiplier),
                Int(blue * multiplier)
            )
        }
        else {
            return String(
                format: "#%02lX%02lX%02lX%02lX",
                Int(red * multiplier),
                Int(green * multiplier),
                Int(blue * multiplier),
                Int(alpha * multiplier)
            )
        }
    }
}

测试示例：

// 获取图片
let image = UIImage(named: "img")!
let width = Int(image.size.width)
let height = Int(image.size.height)
print("图片尺寸：", "(width) * (height)")
         
// 获取指定像素颜色
if let hexString = image[0, 0]?.hexString {
    print("左上角颜色：", hexString)
}
if let hexString = image[width, 0]?.hexString {
    print("右上角颜色：", hexString)
}
if let hexString = image[width/2, height/2]?.hexString {
    print("中间点颜色：", hexString)
}