iphone - 在 iPhone 上从 RGB 更改为 HSB？

Question

我已经用谷歌搜索了很长时间，但找不到这样做的方法。有人有想法吗？有一种 NSColor 方法可以为 mac 执行此操作，但对于 iPhone，我看不到任何内容。我的应用程序中的想法是用户输入 HEX 代码（我已设法进入 RGB）并将其更改为 HSB。

想法？

Answer 1

它只需要一点数学。以下代码只是我为转换创建的自定义类的重要部分。“HSBColor”类只存储色调、饱和度和亮度，如果我需要在系统中实际使用它，我会提供函数来获取它的组件或 UIColor。

注意：除非您定义具有色调、亮度和饱和度属性的 HSBColor 类，否则此代码不会按原样工作。

+(void)max:(int*)max andMin:(int*)min ofArray:(float[])array
{
    *min=0;
    *max=0;
    for(int i=1; i<3; i++)
    {
        if(array[i] > array[*max])
            *max=i;
        if(array[i] < array[*min])
            *min=i;
    }
}

+(HSBColor*)colorWithRed:(float)red Green:(float)green Blue:(float)blue
{
    HSBColor* toReturn = [[[HSBColor alloc] init] autorelease];

    float colorArray[3];
    colorArray[0] = red; 
    colorArray[1] = green; 
    colorArray[2] = blue;
    //NSLog(@"RGB: %f %f %f",colorArray[0],colorArray[1],colorArray[2]);
    int max;
    int min;
    [self max:&max andMin:&min ofArray:colorArray];

    if(max==min)
    {
        toReturn.hue=0;
        toReturn.saturation=0;
        toReturn.brightness=colorArray[0];
    }
    else
    {
        toReturn.brightness=colorArray[max];

        toReturn.saturation=(colorArray[max]-colorArray[min])/(colorArray[max]);

        if(max==0) // Red
            toReturn.hue = (colorArray[1]-colorArray[2])/(colorArray[max]-colorArray[min])*60/360;
        else if(max==1) // Green
            toReturn.hue = (2.0 + (colorArray[2]-colorArray[0])/(colorArray[max]-colorArray[min]))*60/360;
        else // Blue
            toReturn.hue = (4.0 + (colorArray[0]-colorArray[1])/(colorArray[max]-colorArray[min]))*60/360;
    }
    return toReturn;
}

+(HSBColor*)colorWithSystemColor:(UIColor*)color
{

    const CGFloat* components = CGColorGetComponents(color.CGColor);

    return [self colorWithRed:components[0] Green:components[1] Blue:components[2]];
}

Answer 2

如果您需要它：

将 HSV 转换为 RGB（来自 GLPaint 示例应用程序 AppController.m）

//FUNCTIONS:
/*
   HSL2RGB Converts hue, saturation, luminance values to the equivalent red, green and blue values.
   For details on this conversion, see Fundamentals of Interactive Computer Graphics by Foley and van Dam (1982, Addison and Wesley)
   You can also find HSL to RGB conversion algorithms by searching the Internet.
   See also http://en.wikipedia.org/wiki/HSV_color_space for a theoretical explanation
 */
static void HSL2RGB(float h, float s, float l, float* outR, float* outG, float* outB)
{
    float           temp1,
                    temp2;
    float           temp[3];
    int             i;

    // Check for saturation. If there isn't any just return the luminance value for each, which results in gray.
    if(s == 0.0) {
        if(outR)
            *outR = l;
        if(outG)
            *outG = l;
        if(outB)
            *outB = l;
        return;
    }

    // Test for luminance and compute temporary values based on luminance and saturation 
    if(l < 0.5)
        temp2 = l * (1.0 + s);
    else
        temp2 = l + s - l * s;
        temp1 = 2.0 * l - temp2;

    // Compute intermediate values based on hue
    temp[0] = h + 1.0 / 3.0;
    temp[1] = h;
    temp[2] = h - 1.0 / 3.0;

    for(i = 0; i < 3; ++i) {

        // Adjust the range
        if(temp[i] < 0.0)
            temp[i] += 1.0;
        if(temp[i] > 1.0)
            temp[i] -= 1.0;


        if(6.0 * temp[i] < 1.0)
            temp[i] = temp1 + (temp2 - temp1) * 6.0 * temp[i];
        else {
            if(2.0 * temp[i] < 1.0)
                temp[i] = temp2;
            else {
                if(3.0 * temp[i] < 2.0)
                    temp[i] = temp1 + (temp2 - temp1) * ((2.0 / 3.0) - temp[i]) * 6.0;
                else
                    temp[i] = temp1;
            }
        }
    }

    // Assign temporary values to R, G, B
    if(outR)
        *outR = temp[0];
    if(outG)
        *outG = temp[1];
    if(outB)
        *outB = temp[2];
}