我在 Swift 中获取某个像素(由 CGPoint 指定)的像素颜色时遇到了很大的困难。到目前为止，这是我的代码:

@IBOutlet weak var graphImage: UIImageView!

var image : UIImage?

override func viewDidLoad() {
    super.viewDidLoad()
}

func getPixelColor(pos: CGPoint) -> UIColor {
    var pixelData = CGDataProviderCopyData(CGImageGetDataProvider(self.graphImage.image!.CGImage))
    var data : UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData)

    var pixelInfo : Int = ((Int(graphImage.image!.size.width) * Int(pos.y) + Int(pos.x)*4))

    let r = CGFloat(data[pixelInfo]) / CGFloat(255.0)
    let g = CGFloat(data[pixelInfo]+1) / CGFloat(255.0)
    let b = CGFloat(data[pixelInfo]+2) / CGFloat(255.0)
    let a = CGFloat(data[pixelInfo]+3) / CGFloat(255.0)

    return UIColor(red: r, green: g, blue: b, alpha: a)
}

@IBAction func playTapped(sender: AnyObject) {

    getPixelColor(CGPoint(x: 100.0, y: 100.0))

}

我的应用程序在点击播放后崩溃，在“let g = CGFloat...”这一行我没有看到任何错误，尽管我对任何与图像有关的事情都很陌生。我想知道我是否需要使用不同类型的图像，或者我的 pixelInfo 变量中的某些内容是否有误。顺便说一下，我从 How do I get the color of a pixel in a UIImage with Swift? 得到了大部分代码.任何人都可以指出可能是什么问题吗？任何帮助将不胜感激!

最佳答案

jasonnoahchoi给出了一个很好的答案 - 如果您在转换到 Swift 3.0 时遇到问题，请尝试使用相同的代码进行以下更改:

class PixelExtractor: NSObject {
    
    let image: CGImage
    let context: CGContext?
    
    var width: Int {
        get {
            return image.width
        }
    }
    
    var height: Int {
        get {
            return image.height
        }
    }
    
    init(img: CGImage) {
        image = img
        context = PixelExtractor.createBitmapContext(cgImage: img)
    }
    
    class func createBitmapContext(cgImage: CGImage) -> CGContext {
        
        // Get image width, height
        let pixelsWide = cgImage.width
        let pixelsHigh = cgImage.height
        
        let bitmapBytesPerRow = pixelsWide * 4
        let bitmapByteCount = bitmapBytesPerRow * Int(pixelsHigh)
        
        // Use the generic RGB color space.
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        
        // Allocate memory for image data. This is the destination in memory
        // where any drawing to the bitmap context will be rendered.
        let bitmapData = malloc(bitmapByteCount)
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue)
        let size = CGSize(width: pixelsWide, height: pixelsHigh)
        UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
        // create bitmap
        let context = CGContext(data: bitmapData, width: pixelsWide, height: pixelsHigh, bitsPerComponent: 8,
                                bytesPerRow: bitmapBytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)
        
        // draw the image onto the context
        let rect = CGRect(x: 0, y: 0, width: pixelsWide, height: pixelsHigh)
        context?.draw(cgImage, in: rect)
        
        return context!
    }
    
    private func colorAt(x: Int, y: Int) -> UIColor {
        
        assert(0<=x && x<width)
        assert(0<=y && y<height)
        
        let data = context!.data!
        
        let offset = 4 * (y * width + x)
        
        let alpha = CGFloat(data.load(fromByteOffset: offset, as: UInt8.self)) / 255.0
        let red = CGFloat(data.load(fromByteOffset: offset + 1, as: UInt8.self)) / 255.0
        let green = CGFloat(data.load(fromByteOffset: offset + 2, as: UInt8.self)) / 255.0
        let blue = CGFloat(data.load(fromByteOffset: offset + 3, as: UInt8.self)) / 255.0
        
        let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)
        
        return color
    }
}

关于ios - 使用 CGPoint 从图像中获取像素颜色，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35029672/