ios – 如何逐个像素地创建图像

var array = ["w","x","y","w","y"] //there will be like 26 millions of those

您可以创建一个CGContext,然后检索该图像的数据缓冲区,然后使用与您的字符串值对应的值填充该缓冲区：

func createImage(width: Int,height: Int,from array: [String],completionHandler: @escaping (UIImage?,String?) -> Void) {
    DispatchQueue.global(qos: .utility).async {
        let colorSpace       = CGColorSpaceCreateDeviceRGB()
        let bytesPerPixel    = 4
        let bitsPerComponent = 8
        let bytesPerRow      = bytesPerPixel * width
        let bitmapInfo       = RGBA32.bitmapInfo

        guard array.count == width * height else {
            completionHandler(nil,"Array size \(array.count) is incorrect given dimensions \(width) x \(height)")
            return
        }

        guard let context = CGContext(data: nil,width: width,height: height,bitsPerComponent: bitsPerComponent,bytesPerRow: bytesPerRow,space: colorSpace,bitmapInfo: bitmapInfo) else {
            completionHandler(nil,"unable to create context")
            return
        }

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

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

        for (index,String) in array.enumerated() {
            switch String {
            case "w": pixelBuffer[index] = .blue
            case "x": pixelBuffer[index] = .red
            case "y": pixelBuffer[index] = .green
            case "v": pixelBuffer[index] = .black
            default: completionHandler(nil,"Unexpected value: \(String)"); return
            }
        }

        let cgImage = context.makeImage()!

        let image = UIImage(cgImage: cgImagE)

        // or
        //
        // let image = UIImage(cgImage: cgImage,scale: UIScreen.main.scale,orientation: .up)

        completionHandler(image,nil)
    }

}

如果有2600万像素,您可能希望使此异步以避免阻塞主队列.

顺便说一句,上面使用这个结构：

struct RGBA32: Equatable {
    private var color: UInt32

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

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

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

    var alphaComponent: 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
    }

    static let black = RGBA32(red: 0,green: 0,blue: 0,alpha: 255)
    static let red   = RGBA32(red: 255,alpha: 255)
    static let green = RGBA32(red: 0,green: 255,alpha: 255)
    static let blue  = RGBA32(red: 0,blue: 255,alpha: 255)
}

要保存图像,您可以执行以下操作：

createImage(width: width,from: array) { image,errormessage in
    guard let image = image,errormessage == nil else {
        print(errormessage!)
        return
    }

    DispatchQueue.main.async {
        self.imageView.image = image
        UIImageWriteToSavedPhotosAlbum(image,self,#SELEctor(self.image(_:didFinishSavingWithError:contexTinfo:)),nil)
    }
}

哪里

func image(_ image: UIImage,didFinishSavingWithError error: Error?,contexTinfo: Any?) {
    guard error == nil else {
        print(error!.localizedDescription)
        return
    }

    print("image saved")
}