在 0-255 范围内将 RGB 转换为 HSV 和 HSV 到 RGB 的算法

Question

我正在寻找从 RGB 到 HSV 的颜色空间转换器，特别是对于两种颜色空间的 0 到 255 范围。

原文由 jmasterx 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

我已经用了很长时间了——现在不知道它们是从哪里来的……请注意，输入和输出，除了以度为单位的角度外，都在 0 到 1.0 的范围内。

注意：此代码不会对输入进行真正的完整性检查。谨慎行事！

 typedef struct {
    double r;       // a fraction between 0 and 1
    double g;       // a fraction between 0 and 1
    double b;       // a fraction between 0 and 1
} rgb;

typedef struct {
    double h;       // angle in degrees
    double s;       // a fraction between 0 and 1
    double v;       // a fraction between 0 and 1
} hsv;

static hsv   rgb2hsv(rgb in);
static rgb   hsv2rgb(hsv in);

hsv rgb2hsv(rgb in)
{
    hsv         out;
    double      min, max, delta;

    min = in.r < in.g ? in.r : in.g;
    min = min  < in.b ? min  : in.b;

    max = in.r > in.g ? in.r : in.g;
    max = max  > in.b ? max  : in.b;

    out.v = max;                                // v
    delta = max - min;
    if (delta < 0.00001)
    {
        out.s = 0;
        out.h = 0; // undefined, maybe nan?
        return out;
    }
    if( max > 0.0 ) { // NOTE: if Max is == 0, this divide would cause a crash
        out.s = (delta / max);                  // s
    } else {
        // if max is 0, then r = g = b = 0
        // s = 0, h is undefined
        out.s = 0.0;
        out.h = NAN;                            // its now undefined
        return out;
    }
    if( in.r >= max )                           // > is bogus, just keeps compilor happy
        out.h = ( in.g - in.b ) / delta;        // between yellow & magenta
    else
    if( in.g >= max )
        out.h = 2.0 + ( in.b - in.r ) / delta;  // between cyan & yellow
    else
        out.h = 4.0 + ( in.r - in.g ) / delta;  // between magenta & cyan

    out.h *= 60.0;                              // degrees

    if( out.h < 0.0 )
        out.h += 360.0;

    return out;
}

rgb hsv2rgb(hsv in)
{
    double      hh, p, q, t, ff;
    long        i;
    rgb         out;

    if(in.s <= 0.0) {       // < is bogus, just shuts up warnings
        out.r = in.v;
        out.g = in.v;
        out.b = in.v;
        return out;
    }
    hh = in.h;
    if(hh >= 360.0) hh = 0.0;
    hh /= 60.0;
    i = (long)hh;
    ff = hh - i;
    p = in.v * (1.0 - in.s);
    q = in.v * (1.0 - (in.s * ff));
    t = in.v * (1.0 - (in.s * (1.0 - ff)));

    switch(i) {
    case 0:
        out.r = in.v;
        out.g = t;
        out.b = p;
        break;
    case 1:
        out.r = q;
        out.g = in.v;
        out.b = p;
        break;
    case 2:
        out.r = p;
        out.g = in.v;
        out.b = t;
        break;

    case 3:
        out.r = p;
        out.g = q;
        out.b = in.v;
        break;
    case 4:
        out.r = t;
        out.g = p;
        out.b = in.v;
        break;
    case 5:
    default:
        out.r = in.v;
        out.g = p;
        out.b = q;
        break;
    }
    return out;
}

原文由 David H 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

在解释了颜色转换的所有算法之后，这是一个带有文章的 在线转换器。

您可能更喜欢现成的 C 版本，但应用时间不长，它可以帮助其他人尝试用另一种语言或另一种色彩空间做同样的事情。

原文由 Mig 发布，翻译遵循 CC BY-SA 4.0 许可协议