Color conversion scripts

From Second Life Wiki

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=360;
     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;
}