如何不使深灰色变成透明,从而从图像中删除背景 [英] How to not cause dark gray color to be transparent removing background from image
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问题描述
我遇到一个问题,当我尝试从图像(在这种情况下为图像背景)中去除绿色,但所有深灰色(在我要保留的图像部分内)变成半透明的.我不确定为什么要提出以下建议:
I'm having an issue where when I try to remove the green from an image (in this case the image background) but all the dark grays (within the part of the image I want to keep) become semi-transparent. I am unsure why, would like some advice on how to:
func chromaKeyFilter(fromHue: CGFloat, toHue: CGFloat) -> CIFilter? {
let size = 64
var cubeRGB = [Float]()
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)
let color = UIColor(red: red, green: green, blue: blue, alpha: 1)
let hueColor = color.hsbColor
let alpha: CGFloat = (hueColor.hue >= fromHue && hueColor.hue <= toHue) ? 0 : 1
cubeRGB.append(Float(red * alpha))
cubeRGB.append(Float(green * alpha))
cubeRGB.append(Float(blue * alpha))
cubeRGB.append(Float(alpha))
}
}
}
let data = Data(bytes: cubeRGB, count: cubeRGB.count * MemoryLayout<Float>.size)
let params: [String: Any] = ["inputCubeDimension": size, "inputCubeData": data]
return CIFilter(name: "CIColorCube", parameters: params)
}
func filterPixels(foregroundCIImage: CIImage) -> CIImage {
let chromaCIFilter = self.chromaKeyFilter(fromHue: 0.33, toHue: 0.34)
chromaCIFilter?.setValue(foregroundCIImage, forKey: kCIInputImageKey)
let sourceCIImageWithoutBackground = chromaCIFilter?.outputImage
var image = CIImage()
if let filteredImage = sourceCIImageWithoutBackground {
image = filteredImage
}
return image
}
}
extension UIColor {
/// Decomposes UIColor to its HSBA components
var hsbColor: HSBColor {
var h: CGFloat = 0, s: CGFloat = 0, b: CGFloat = 0, a: CGFloat = 0
self.getHue(&h, saturation: &s, brightness: &b, alpha: &a)
return HSBColor(hue: h, saturation: s, brightness: b, alpha: a)
}
/// Holds the CGFloat values of HSBA components of a color
public struct HSBColor {
var hue: CGFloat
var saturation: CGFloat
var brightness: CGFloat
var alpha: CGFloat
}
}
样本图片:
推荐答案
您的代码是正确的,但请记住,深灰色可能确实是非常深的绿色.
Your code is correct, but remember that a dark gray could really be a very dark green.
在这一行:
let alpha: CGFloat = (hueColor.hue >= fromHue && hueColor.hue <= toHue) ? 0 : 1
我会考虑亮度/饱和度.例如
I would take brightness/saturation into account. For example
let alpha: CGFloat = (hueColor.saturation > 0.1 && hueColor.hue >= fromHue && hueColor.hue <= toHue) ? 0 : 1
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