色度键的平滑边缘-CoreImage-码文网

我使用下面的代码从图像中删除绿色背景。但是图像的边缘有绿调，一些像素被损坏。

 func chromaKeyFilter(fromHue: CGFloat, toHue: CGFloat) -> CIFilter?
    {
        // 1
        let size = 64
        var cubeRGB = [Float]()
        // 2
        for z in 0 ..< size {
            let blue = CGFloat(z) / CGFloat(size-1)
            for y in 0 ..< size {
                let green = CGFloat(y) / CGFloat(size-1)
                for x in 0 ..< size {
                    let red = CGFloat(x) / CGFloat(size-1)
                    // 3
                    let hue = getHue(red: red, green: green, blue: blue)
                    let alpha: CGFloat = (hue >= fromHue && hue <= toHue) ? 0: 1
                    // 4
                    cubeRGB.append(Float(red * alpha))
                    cubeRGB.append(Float(green * alpha))
                    cubeRGB.append(Float(blue * alpha))
                    cubeRGB.append(Float(alpha))
                }
            }
        }
  @IBAction func clicked(_ sender: Any) {
          let a = URL(fileURLWithPath:"green.png")
          let b = URL(fileURLWithPath:"back.jpg")
        let image1 = CIImage(contentsOf: a)
        let image2 = CIImage(contentsOf: b)
        let chromaCIFilter = self.chromaKeyFilter(fromHue: 0.3, toHue: 0.4)
        chromaCIFilter?.setValue(image1, forKey: kCIInputImageKey)
        let sourceCIImageWithoutBackground = chromaCIFilter?.outputImage
        /*let compositor = CIFilter(name:"CISourceOverCompositing")
        compositor?.setValue(sourceCIImageWithoutBackground, forKey: kCIInputImageKey)
        compositor?.setValue(image2, forKey: kCIInputBackgroundImageKey)
        let compositedCIImage = compositor?.outputImage*/
        var rep: NSCIImageRep = NSCIImageRep(ciImage: sourceCIImageWithoutBackground!)
        var nsImage: NSImage = NSImage(size: rep.size)
        nsImage.addRepresentation(rep)
        let url = URL(fileURLWithPath:"file.png")
        nsImage.pngWrite(to: url)
        super.viewDidLoad()
    }

输入:

Output:

Update:

Update 2:

Update 3:

用于色度键控的专业工具通常包括所谓的溢出抑制器。溢出抑制器查找包含少量色度键颜色的像素，并将颜色向相反方向移动。因此，绿色像素将向品红色移动。这减少了您经常在键控素材周围看到的绿色条纹。

例如,您可以找到当前像素的色相与fromHue和toHue之间的角距离,并执行以下操作:

// Get the distance from the edges of the range, and convert to be between 0 and 1
var distance: CGFloat
if (fromHue <= hue) && (hue <= toHue) {
    distance = min(abs(hue - fromHue), abs(hue - toHue)) / ((toHue - fromHue) / 2.0)
} else {
    distance = 0.0
}
distance = 1.0 - distance
let alpha = sin(.pi * distance - .pi / 2.0) * 0.5 + 0.5

这将为您提供从范围边缘到范围中心的平滑变化。（请注意，我已经停止处理色调在 360 ° 处环绕的事实。这是您必须处理的事情。）衰减的图形如下所示：

您可以做的另一件事是将键控限制为仅影响饱和度高于某个阈值并且值高于某个阈值的像素。对于非常暗和 / 或不饱和的颜色，您可能不想将其淘汰。例如，我认为这将有助于解决您在模型夹克上看到的问题。

My (live) keyer works like this (with the enhancements user1118321 describes) and using its yser I quickly noticed this is most likely not a true green screen image. It's one of many fake ones where the green screen seems to have been replaced with a saturated monochrome green. Though this may look nice, it introduces artefacts where the keyed subject (with fringes of the originally used green) meets the monochrome green. You can see a single green was used by looking at the histogram. Real green screen always have (in)visible shades of green. I was able to get a decent key but had to manually tweak some settings. With a NLE you can probably get much better results, but they will also be a lot more complex. So to get back to your issue, your code probably works as it is now (update #3), you just have to use a proper real life green screen image.