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Question

我正在创建一个应用程序来更改地图上的颜色以突出显示某个国家/地区。它就像一个代码系统，其中一个国家将具有特定的颜色，如果条件允许，该颜色将变为黄色，其余颜色将变为绿色。它类似于标记系统，根据用户输入突出显示特定国家/地区。我之前看到过这个帖子，我修改了它，所以它可以使用参数作为检测颜色。 https://codedump.io/share/gEsdbwFbGT3T/1/change-color-of-certain-pixels-in-a-uiimage

这是修改后的代码：

func processPixelsInImage(inputImage: UIImage, r: UInt8, b: UInt8, g: UInt8) -> UIImage {
        let inputCGImage     = inputImage.CGImage
        let colorSpace       = CGColorSpaceCreateDeviceRGB()
        let width            = CGImageGetWidth(inputCGImage)
        let height           = CGImageGetHeight(inputCGImage)
        let bytesPerPixel    = 4
        let bitsPerComponent = 8
        let bytesPerRow      = bytesPerPixel * width
        let bitmapInfo       = CGImageAlphaInfo.PremultipliedFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue

        let context = CGBitmapContextCreate(nil, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo)!
        CGContextDrawImage(context, CGRectMake(0, 0, CGFloat(width), CGFloat(height)), inputCGImage)

        let pixelBuffer = UnsafeMutablePointer<UInt32>(CGBitmapContextGetData(context))

        var currentPixel = pixelBuffer

        for _ in 0 ..< Int(height) {
            for _ in 0 ..< Int(width) {
                let pixel = currentPixel.memory

                if red(pixel) == r && green(pixel) == g && blue(pixel) == b {
                    currentPixel.memory = rgba(red: 0, green: 170, blue: 0, alpha: 255)
                }
                currentPixel = currentPixel.successor()
            }
        }

        let outputCGImage = CGBitmapContextCreateImage(context)
        let outputImage = UIImage(CGImage: outputCGImage!, scale: inputImage.scale, orientation: inputImage.imageOrientation)

        return outputImage
    }

    func alpha(color: UInt32) -> UInt8 {
        return UInt8((color >> 24) & 255)
    }

    func red(color: UInt32) -> UInt8 {
        return UInt8((color >> 16) & 255)
    }

    func green(color: UInt32) -> UInt8 {
        return UInt8((color >> 8) & 255)
    }

    func blue(color: UInt32) -> UInt8 {
        return UInt8((color >> 0) & 255)
    }

    func rgba(red red: UInt8, green: UInt8, blue: UInt8, alpha: UInt8) -> UInt32 {
        return (UInt32(alpha) << 24) | (UInt32(red) << 16) | (UInt32(green) << 8) | (UInt32(blue) << 0)
    }

当我使用除黑色（0,0,0）以外的RGB值时，它不会检测并更改颜色。我不确定它是否与rgb值的普通CG颜色相比是不同的缩放因为不同的数据类型但我仍然不确定如何完全使用此功能。如何使用RGB值检测黑色以外的颜色并将其更改为另一个？

Answer 1

我调整了类似的代码，将所有UIImage白色像素更改为清晰像素

（斯威夫特3）

func processPixelsInImage(_ image: UIImage) -> UIImage? {
guard let inputCGImage = image.cgImage else {
    //print("unable to get cgImage")
    return nil
}
let colorSpace       = CGColorSpaceCreateDeviceRGB()
let width            = inputCGImage.width
let height           = inputCGImage.height
let bytesPerPixel    = 4
let bitsPerComponent = 8
let bytesPerRow      = bytesPerPixel * width
let bitmapInfo       = RGBA32.bitmapInfo

guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo) else {
    //print("unable to create context")
    return nil
}
context.draw(inputCGImage, in: CGRect(x: 0, y: 0, width: width, height: height))

guard let buffer = context.data else {
    //print("unable to get context data")
    return nil
}

let pixelBuffer = buffer.bindMemory(to: RGBA32.self, capacity: width * height)

let white = RGBA32(red: 255, green: 255, blue: 255, alpha: 255)
let clear = RGBA32(red: 0, green: 0, blue: 0, alpha: 0)

for row in 0 ..< Int(height) {
    for column in 0 ..< Int(width) {
        let offset = row * width + column
        if pixelBuffer[offset] == white {
            pixelBuffer[offset] = clear
        }
    }
}

let outputCGImage = context.makeImage()!
let outputImage = UIImage(cgImage: outputCGImage, scale: image.scale, orientation: image.imageOrientation)

return outputImage

}


struct RGBA32: Equatable {
var color: UInt32

var red: UInt8 {
    return UInt8((color >> 24) & 255)
}

var green: UInt8 {
    return UInt8((color >> 16) & 255)
}

var blue: UInt8 {
    return UInt8((color >> 8) & 255)
}

var alpha: UInt8 {
    return UInt8((color >> 0) & 255)
}

init(red: UInt8, green: UInt8, blue: UInt8, alpha: UInt8) {
    color = (UInt32(red) << 24) | (UInt32(green) << 16) | (UInt32(blue) << 8) | (UInt32(alpha) << 0)
}

static let bitmapInfo = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Little.rawValue

static func ==(lhs: RGBA32, rhs: RGBA32) -> Bool {
    return lhs.color == rhs.color
}

}