Color conversion scripts

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The following functions convert between LSL color in Red Green Blue (RGB) format and color in Hue Saturation Value (HSV) format. The functions are based on "c" algorithms from c color conversion but required some debugging and extensive re-working to fit them in to LSL. For a discussion of HSV color format please see the wikipedia entry at HSV Color


RGB to HSV

// by [[Sally LaSalle]], code released to the public domain under GNU GPL version 3.0 license.
// you are free to use, and you are free to donate to me if you wish!! :P

// takes an RGB color as a vector, with range <float R[0,1], float G[0,1], float B[0,1]>
// returns a vector with HSV ranged from <float H[0,360], float S[0,1],  float V[0,1]>
// H ranges smoothly from Red=0, Yellow=60, Green=120, Cyan=180, Blue=240, Violet=300 and back to Red

vector RGBtoHSV( vector rgb )
{
    float R = rgb.x;
    if (R<0)		// catch malformed input
        R=0;
    else if (R>1)
        R=1;
    float G = rgb.y;
    if (G<0)		// catch malformed input
        G=0;
    else if (G>1)
        G=1;
    float B = rgb.z;
    if (B<0)		// catch malformed input
        B=0;
    else if (B>1)
        B=1;
    
    float H;
    float S;
    float V;
    
    list rgbList = [R, G, B]; // list used to get min and max
        
    float min;
    float max;
    float achromatic;  // =1 if R=G=B
    float delta;
    
    vector hsv;  // the return HSV vector

    min = llListStatistics(LIST_STAT_MIN, rgbList); //MIN of ( R, G, B );
    max = llListStatistics(LIST_STAT_MAX, rgbList); //MAX of ( R, G, B );
    if (R==G && G==B)
        achromatic = 1;  // it is a shade of grey, white or black
    else
        achromatic = 0;

    V = max;                    // V = brightness Value form 0 to 1
    delta = max - min;

    if( max != 0 )
        S = delta / max;        // S = saturation from 0 to 1
    else {
        // R = G = B = 0        // S = 0, V = 0, H = 0
        S = 0;                  
        V = 0;                  
        H = 0;
        
        hsv.x = H;
        hsv.y = S;
        hsv.z = V;
        return hsv;             //H = S = V = 0
    }

    if (achromatic == 1)
        H = 0;
    else if( R == max )
        H = 0 + ( G - B ) / delta;    // between red & yellow
    else if( G == max )
        H = 2 + ( B - R ) / delta;    // between yellow & cyan
    else
        H = 4 + ( R - G ) / delta;    // between cyan & red
    

    H *= 60;                	      // H is traditionally a figure between 0 and 360 degrees
    if( H < 0 )
        H += 360;

    hsv.x = H;
    hsv.y = S;
    hsv.z = V;
    return hsv;
}


HSV to RGB

// by Sally LaSalle, code released to the public domain under GNU GPL version 3.0 license.
// you are free to use, and you are free to donate to me if you wish!! :P

// takes a vector encoded Hue Saturation Value (HSV) triplet
// HSV should be entered with floats the ranges: <float H(0 to 360), float S(0 to 1),float V(0 to 1)>
// And Returns a vector encode Red Green Blue (RGB) color triplet
// RGB will be returned with floats in ranges <float R(0 to 1),float G(0 to 1),float B(0 to 1)>

vector HSVtoRGB( vector hsv )
{
    integer i;
	
     float H = hsv.x;
     if (H<0)		// catch malformed H input
	H=0;
     else if (H>=360)
	H=0;
     float S = hsv.y;
     if (S<0)		// catch malformed S input
	S=0;
     else if (S>1)
	S=1;
     float V = hsv.z;
     if (V<0)		// catch malformed V input
	V=0;
     else if (V>1)
	V=1;

    float R;
    float G;
    float B;
    
    float f; 	    // variables for calculating base color mixing around the "spectrum circle"
    float p;
    float q;
    float t;
  
    vector rgb;
    
    if( S == 0 ) {  // achromatic (grey) simply set R,G, & B = Value
        R = V;
        G = V;
        B = V;

        rgb.x = R;
        rgb.y = G;
        rgb.z = B;
        return rgb;
    }

    H /= 60;              // Hue factored into range 0 to 5
    i = llFloor( H );	  // integer floor of Hue
    f = H - i;            // factorial part of H

    p = V * ( 1 - S );
    q = V * ( 1 - S * f );
    t = V * ( 1 - S * ( 1 - f ) );

    if (i==0){
        R = V;
        G = t;
        B = p;
    } else if (i==1){
        R = q;
        G = V;
        B = p;
    } else if (i==2){
        R = p;
        G = V;
        B = t;
    } else if (i==3){
        R = p;
        G = q;
        B = V;
    } else if (i==4){
        R = t;
        G = p;
        B = V;
    } else {       
        R = V;
        G = p;
        B = q;
    }
   
    rgb.x = R;
    rgb.y = G;
    rgb.z = B;
    
    return rgb;
}

HSL to RGB

//HSL to RGB conversion function. By Cobalt Arkright. Released to the public under GNU GPL version 3.0 license.
//Takes a vector encoded HSL triplet and outputs a vector encoded RGB triplet.

//Input values should be in the following ranges: <float H(0 to 1), float S(0 to 1), float L(0 to 1)>. In this case, set h360 to "false."
//If you wish to use H(0 to 360), leave the boolean value "h360" set to true.

//Edit 12/27/2009: Cleaned up readability, played around a little bit with value calculation, and hopefully everything is more accurate now. failthfulll Moonwall brought it to my attention that the script wasn't working properly when using H ranges of 0 to 360. Based on my testing, it works now. If anyone else has a problem, feel free to PM me.

vector HSLtoRGB (vector hsl){
    integer h360 = TRUE;
    
    if (h360){
        //Catch malformed H input for H(0 to 360)
        if (hsl.x < 0)
            hsl.x = 0;

        else if (hsl.x > 360)
            hsl.x = 360;
        hsl.x = hsl.x / 360;
    }

    else{
        //Catch malformed H input for H(0 to 1)
        if (hsl.x < 0) 
            hsl.x = 0;

        else if (hsl.x > 1.0) 
            hsl.x = 1.0;
    }
 
    //Catch malformed S input
    if (hsl.y < 0)
        hsl.y = 0;

    else if (hsl.y > 1.0)
        hsl.y = 1.0;
 
    //Catch malformed L input
    if (hsl.z < 0)
        hsl.z = 0;

    else if (hsl.z > 1.0)
        hsl.z = 1.0;
 
    //Declare required variables
    vector rgb;
    float q;
    float p;
    float tr;
    float tg;
    float tb;
 
    //Special case: When S = 0, the result is monochromatic, and R = B = G = L.
    if (hsl.y == 0){
        rgb.x = rgb.y = rgb.z = hsl.z;
        return rgb;
    }
 
    //Set up temporary values for conversion
    if (hsl.z < 0.5)
        q = hsl.z * (1.0 + hsl.y);

    else if (hsl.z >= 0.5) 
        q = hsl.z + hsl.y - (hsl.z * hsl.y);
    
    p = 2 * hsl.z - q;
    
    tr = hsl.x + (1.0 / 3.0);
    tg = hsl.x;
    tb = hsl.x - (1.0 / 3.0);
 
    //Normalize temporary R value
    if (tr < 0)
        tr = tr + 1.0;
    
    else if (tr > 1.0)
        tr = tr - 1.0;
 
    //Normalize temporary G value
    if (tg < 0)
        tg = tg + 1.0;
    
    else if (tg > 1.0)
        tg = tg - 1.0;
 
    //Normalize temporary B value
    if (tb < 0)
        tb = tb + 1.0;
    
    else if (tb > 1.0)
        tb = tb - 1.0;
 

    //Calculate R value
    if (tr < (1.0 / 6.0))
        rgb.x = p + ((q - p) * 6 * tr);
    
    else if ((1.0 / 6.0) <= tr && tr < 0.5)
        rgb.x = q;
    
    else if (0.5 <= tr && tr < (2.0 / 3.0))
        rgb.x = p + ((q - p) * 6 * ((2.0 / 3.0) - tr));
    
    else
        rgb.x = p;
 
    //Calculate G value
    if (tg < (1.0 / 6.0))
        rgb.y = p + ((q - p) * 6 * tg);
    
    else if ((1.0 / 6.0) <= tg && tg < 0.5)
        rgb.y = q;
    
    else if (0.5 <= tg && tg < (2.0 / 3.0))
        rgb.y = p + (( q - p) * 6 * ((2.0 / 3.0) - tg));
    
    else
        rgb.y = p;
 
    //Caluclate B value
    if (tb < (1.0 / 6.0))
        rgb.z = p + ((q - p) * 6 * tb);
    
    else if ((1.0 / 6.0) <= tb && tb < 0.5)
        rgb.z = q;
    
    else if (0.5 <= tb && tb < (2.0 / 3.0))
        rgb.z = p + ((q - p) * 6 * ((2.0 / 3.0) - tb));
    
    else 
        rgb.z = p;
 
    //Return the result
    return rgb;
}

Amazing what a little bit of readability does. If I ever submit anything else that poorly formatted again, someone please smack me upside the head and tell me to come fix it, please.

HSV to HSL

For more info about the difference between HSL and HSV, see the wikipedia entry: HSL and HSV

Original code most likely from: converting-between-hsl-and-hsv.html 

// Convert from HSV (hue, saturation, value) to HSL (hue, saturation, luminosity)
// Created by Michaelangelo David code released to the public domain under GNU GPL version 3.0 license.

vector hsv_to_hsl( vector HSV )
{
     vector HSL;  
     
     HSL.x = HSV.x;
     HSL.z = (2 - HSV.y) * HSV.z;
     HSL.y = HSV.y * HSV.z;
     if (HSL.z <= 1) HSL.y /= HSL.z;
     else HSL.y /= (2 - HSL.z);
     HSL.z /= 2;
     
     return HSL;
}

HSL to HSV

// Convert from HSL (hue, saturation, luminosity) to HSV (hue, saturation, value)
// Created by Michaelangelo David, code released to the public domain under GNU GPL version 3.0 license.
vector hsl_to_hsv( vector HSL )
{
     vector HSV;  
     HSV.x = HSL.x;
     HSL.z *= 2;
     if (HSL.z <= 1) HSL.y *= HSL.z;
     else HSL.y *= ( 2 - HSL.z);
     
     HSV.z = (HSL.z + HSL.y) / 2;
     HSV.y = (2 * HSL.y) / (HSL.z + HSL.y);
     
     return HSV;
}

HSL to RGB

I wrote the following two functions since the RGBtoHSL By Cobalt Arkright had a strange bug (math error) when some values was passed to the functions. And I couldn't find a reverse function for RGB to HSL. I tried to find out where the error was but I didn't succeded in fixing it so i wrote them from the beginning with a different approach. The functions are similar however, just something different in the coding. 

// HSL to RGB conversion function. By Clematide Oyen (Laura Aastha Bondi).
// Inspired by a function written by Alec Thilenius in this article: http://stackoverflow.com/questions/2353211/hsl-to-rgb-color-conversion
// Released to the public under GNU GPL version 3.0 license.
// Takes a vector encoded HSL triplet and outputs a vector encoded RGB triplet.
// Input HSL values should be in the standard format used in the LSL with the following ranges: <float H (0 to 1), float S (0 to 1), float L (0 to 1)>.
// Output is RGB values in the standard format used in the LSL with the following ranges: <float R (0 to 1), float G (0 to 1), float B (0 to 1)>.

vector HslToRgb(vector hsl)
{
    float r;
    float g;
    float b;

    if (hsl.y == 0.0) // If saturation is 0 the image is monochrome
        r = g = b = hsl.z;
    else
    {
        float q;
        if (hsl.z < 0.5)
            q = hsl.z * (1.0 + hsl.y);
        else
            q = hsl.z + hsl.y - hsl.z * hsl.y;
        
        float p = 2.0 * hsl.z - q;
        
        r = HueToRgb(p, q, hsl.x + 1.0 / 3.0);
        g = HueToRgb(p, q, hsl.x);
        b = HueToRgb(p, q, hsl.x - 1.0 / 3.0);
    }
    return <(r), (g), (b)>;
}

float HueToRgb(float p, float q, float t)
{
    if (t < 0.0) t += 1.0;
    if (t > 1.0) t -= 1.0;
    if (t < 1.0 / 6.0) return p + (q - p) * 6.0 * t;
    if (t < 1.0 / 2.0) return q;
    if (t < 2.0 / 3.0) return p + (q - p) * (2.0 / 3.0 - t) * 6.0;
    return p;
}

RGB to HSL

// RGB to HSL conversion function. By Clematide Oyen (Laura Aastha Bondi).
// Inspired by a function written by Alec Thilenius in this article: http://stackoverflow.com/questions/2353211/hsl-to-rgb-color-conversion
// Released to the public under GNU GPL version 3.0 license.
// Takes a vector encoded RGB triplet and outputs a vector encoded HSL triplet.
// Input RGB values should be in the standard format used in the LSL with the following ranges: <float R (0 to 1), float G (0 to 1), float B (0 to 1)>.
// Output is HSL values in the standard format used in the LSL with the following ranges: <float H (0 to 1), float S (0 to 1), float L (0 to 1)>.

vector RgbToHsl(vector rgb)
{
    float r = rgb.x;
    float g = rgb.y;
    float b = rgb.z;
    float h;
    float s;
    float l;
    float max;
    float min;

    // Looking for the max value among r, g and b
    if (r > g && r > b) max= r;
    else if (g > b) max = g;
    else max = b;
    
    // Looking for the min value among r, g and b
    if (r < g && r < b) min = r;
    else if (g < b) min = g;
    else min = b;

    l = (max + min) / 2.0;
    
    if (max == min)
    {
        h = 0.0;
        s = 0.0;
    }
    else
    {
        float d = max - min;

        if (l > 0.5) s = d / (2.0 - max - min);
        else s = d / (max + min);
        
        if (max == r) {
            if (g < b) h = (g - b) / d + 6.0;
            else h = (g - b) / d;
        }
        else if (max == g)
            h = (b - r) / d + 2.0;
        else
            h = (r - g) / d + 4.0;
        h /= 6.0;
    }

    return <h, s, l>;
}
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