从UIImage中删除颜色

import UIKit

func removeColorFromImage(image: UIImage, colorToRemove: UIColor) -> UIImage? {
    guard let cgImage = image.cgImage else {
        return nil
    }
    
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let width = cgImage.width
    let height = cgImage.height
    let bytesPerPixel = 4
    let bytesPerRow = bytesPerPixel * width
    let bitsPerComponent = 8
    let bitmapInfo = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Big.rawValue
    
    guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo) else {
        return nil
    }
    
    context.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))
    
    let pixelData = context.data
    let data = UnsafeMutablePointer<UInt8>.allocate(capacity: width * height * bytesPerPixel)
    data.initialize(repeating: 0, count: width * height * bytesPerPixel)
    data.assign(from: pixelData!.assumingMemoryBound(to: UInt8.self), count: width * height * bytesPerPixel)
    
    let colorComponents = colorToRemove.cgColor.components!
    let red = colorComponents[0] * 255
    let green = colorComponents[1] * 255
    let blue = colorComponents[2] * 255
    
    for i in 0..<(width * height * bytesPerPixel) {
        let alphaIndex = i + 3
        let redIndex = i
        let greenIndex = i + 1
        let blueIndex = i + 2
        
        let alpha = data[alphaIndex]
        let redValue = data[redIndex]
        let greenValue = data[greenIndex]
        let blueValue = data[blueIndex]
        
        if redValue == UInt8(red) && greenValue == UInt8(green) && blueValue == UInt8(blue) {
            data[alphaIndex] = 0 // 设置透明色
        }
    }
    
    let outputContext = CGContext(data: data, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo, releaseCallback: nil, releaseInfo: nil)
    guard let outputCGImage = outputContext?.makeImage() else {
        return nil
    }
    
    let outputImage = UIImage(cgImage: outputCGImage)
    
    return outputImage
}

// 使用示例
let originalImage = UIImage(named: "example.png")
let colorToRemove = UIColor.red
let processedImage = removeColorFromImage(image: originalImage, colorToRemove: colorToRemove)

// 将processedImage显示在UIImageView中或保存到相册中等操作