objective-c - 将 Obj-C RGBtoHSV() 函数转换为 Swift。 min = MIN( r, MIN(g, b )); ETC

Question

有人可以帮我实现这个功能吗？此功能位于相机应用程序内部，该应用程序使用过滤算法来检测颜色变化等方面的差异。语法对我来说非常困难。我不知道如何处理参数中的指针、最小和最大变量语法、什么是增量等？有人可以帮我翻译吗？非常感激。

我还应该用 UIColor 做些什么吗？下面有人提到了。我不知道如何转换。

// r,g,b values are from 0 to 1 // h = [0,360], s = [0,1], v = [0,1]
//  if s == 0, then h = -1 (undefined)

void RGBtoHSV( float r, float g, float b, float *h, float *s, float *v ) {
float min, max, delta;
min = MIN( r, MIN(g, b ));
max = MAX( r, MAX(g, b ));
*v = max;
delta = max - min;
if( max != 0 )
    *s = delta / max;
else {
    // r = g = b = 0
    *s = 0;
    *h = -1;
    return;
}
if( r == max )
    *h = ( g - b ) / delta;
else if( g == max )
    *h=2+(b-r)/delta;
else
    *h=4+(r-g)/delta;
*h *= 60;
if( *h < 0 )
    *h += 360;
}

快速翻译尝试

// r,g,b values are from 0 to 1 // h = [0,360], s = [0,1], v = [0,1]
    //  if s == 0, then h = -1 (undefined)

    func RGBtoHSV(r:Float, g:Float, b:Float, h:Float, s:Float, v:Float) {
        var min:Float = 0.0
        var max:Float = 0.0
        var delta:Float = 0.0

        min = MIN(r, MIN(g, b))
        max = MAX(r, MAX(g, b))

        var v = max
        delta = max - min

        if max != 0 {
           var s = delta / max
        }
        else{
            // r = g = b = 0
            var s = 0
            var h = -1
            return
        }

        if r == max {
            var h = (g - b) / delta
        }
        else if (g == max) {
            var h = 2 + (b - r ) / delta
        }
        else{
            var h = 4 + (r - g) / delta
            var h = 60
        }
        if (h < 0) {
            var h += 360    // how to deal with all of these pointers here in the original Obj-C function above?
        }
    }

Answer 1

Swift 相当于传递一个指针(变量的地址)是一个“输入参数”:

func RGBtoHSV(r : Float, g : Float, b : Float, inout h : Float, inout s : Float, inout v : Float) {
    let rgbMin = min(r, g, b)
    let rgbMax = max(r, g, b)
    let delta = rgbMax - rgbMin

    v = rgbMax
    s = delta/rgbMax
    h = Float(0.0) // Replace by your actual calculation
}

这将被称为

let r : Float = 0.3
let g : Float = 0.5
let b : Float = 0.7

var h : Float = 0.0
var s : Float = 0.0
var v : Float = 0.0

RGBtoHSV(r, g, b, &h, &s, &v)
println([h, s, v])

但是在 Swift 中有一个更好的方法来返回多个值:您可以返回一个元组:

func RGBtoHSV(r : Float, g : Float, b : Float) -> (h : Float, s : Float, v : Float) {
    let rgbMin = min(r, g, b)
    let rgbMax = max(r, g, b)
    let delta = rgbMax - rgbMin

    let v = rgbMax
    let s = delta/rgbMax
    let h = Float(0.0)  // Replace by your actual calculation

    return (h, s, v)
}

这将被称为

let r : Float = 0.3
let g : Float = 0.5
let b : Float = 0.7
let (h, s, v) = RGBtoHSV(r, g, b)
println([h, s, v])

请注意，在 iOS 上，您可以简单地使用 UIColor 类来转换RGB 和 HSV (== HSB) 之间:

func RGBtoHSV(r : CGFloat, g : CGFloat, b : CGFloat) -> (h : CGFloat, s : CGFloat, v : CGFloat) {
    var h : CGFloat = 0.0
    var s : CGFloat = 0.0
    var v : CGFloat = 0.0
    let col = UIColor(red: r, green: g, blue: b, alpha: 1.0)
    col.getHue(&h, saturation: &s, brightness: &v, alpha: nil)
    return (h, s, v)
}

(或使用来自 What is the best/shortest way to convert a UIColor to hex (web color) in Swift? )