Question

我的应用程序中有一个CGColor，我想从中获取色调，饱和度和亮度值。我怎么能访问这些？

Answer 1

请参阅Duncan Champney发表的cocoa-dev帖子"Here is code to Convert RGB <-> HSB"。在那里，他给出了这段代码：

//------------------
//---header file
#define RETURN_HSV(h, s, v) {HSV.H = h; HSV.S = s; HSV.V = v; return
HSV;}

#define RETURN_RGB(r, g, b) {RGB.R = r; RGB.G = g; RGB.B = b; return
RGB;}

#define UNDEFINED 0

// Theoretically, hue 0 (pure red) is identical to hue 6 in these
transforms. Pure

// red always maps to 6 in this implementation. Therefore UNDEFINED
can be

// defined as 0 in situations where only unsigned numbers are desired.

typedef struct {float R, G, B;} RGBType;

typedef struct {float H, S, V;} HSVType;
//------------------
//--The code
#include <math.h>

HSVType RGB_to_HSV( RGBType RGB )
    {
    // RGB are each on [0, 1]. S and V are returned on [0, 1] and H is
    // returned on [0, 1]. Exception: H is returned UNDEFINED if S==0.
    float R = RGB.R, G = RGB.G, B = RGB.B, v, x, f;
    int i;
    HSVType HSV;
    //x = fminx(R, G, B);
    x = fminf(R, G);
    x = fminf(x, B);
    //v = fmaxf(R, G, B);
    v = fmaxf(R, G);
    v = fmaxf(v, B);
    if(v == x) RETURN_HSV(UNDEFINED, 0, v);
    f = (R == x) ? G - B : ((G == x) ? B - R : R - G);
    i = (R == x) ? 3 : ((G == x) ? 5 : 1);
    RETURN_HSV(((i - f /(v - x))/6), (v - x)/v, v);
    }

RGBType HSV_to_RGB( HSVType HSV )
    {
    // H is given on [0, 1] or UNDEFINED. S and V are given on [0, 1].
    // RGB are each returned on [0, 1].
    float h = HSV.H * 6, s = HSV.S, v = HSV.V, m, n, f;
    int i;
    RGBType RGB;
    if (h == 0) h=.01;
    if(h == UNDEFINED) RETURN_RGB(v, v, v);
    i = floorf(h);
    f = h - i;
    if(!(i & 1)) f = 1 - f; // if i is even
    m = v * (1 - s);
    n = v * (1 - s * f);
    switch (i)
        {
        case 6:
        case 0: RETURN_RGB(v, n, m);
        case 1: RETURN_RGB(n, v, m);
        case 2: RETURN_RGB(m, v, n);
        case 3: RETURN_RGB(m, n, v);
        case 4: RETURN_RGB(n, m, v);
        case 5: RETURN_RGB(v, m, n);
        }
    RETURN_RGB(0, 0, 0);
    }
//------------------

如何从CGColor中检索HSB？

1 个答案: