CFLib.org – Common Function Library Project

Description:
Convert an HSL (hue, saturation, luminance) triplet to a hex triplet. This is the reverse of the HextoHSL function, taking an HSL triplet in the form of a list of three values between 0 and 1, and building a hex RGB triplet of the familiar form "xxxxxx".

Return Values:
Returns a string.

Example:

<cfoutput>
Red (HSL: 0,1,0.5) is #HSLtoHex(0,1,0.5)# in hex RGB<br>
Pink (HSL: 0,1,0.875) is #HSLtoHex(0,1,0.875)# in hex RGB<br>
</cfoutput>

Parameters:

Full UDF Source:

/**
 * Convert an HSL (hue, saturation, luminance) triplet to a hex RGB triplet.
 * 
 * @param h      Hue value between 0 and 1.  Decimals must have a leading zero. 
 * @param s      Saturation value between 0 and 1.  Decimals must have a leading zero. 
 * @param l      Luminosityvalue between 0 and 1.  Decimals must have a leading zero. 
 * @return Returns a string. 
 * @author Matthew Walker (matthew@electricsheep.co.nz) 
 * @version 1, November 6, 2001 
 */
function HSLtoHex(H,S,L) {
    // ref Foley and van Dam, Fundamentals of Interactive Computer Graphics
    var R = L;
    var G = L;
    var B = L;
        Var temp1=0;
        Var temp2=0;
        Var Rtemp3=0;
        Var Gtemp3=0;
        Var Btemp3=0;
        Var Rhex=0;
        Var Ghex=0;
        Var Bhex=0;
    if ( S ) {
        if ( L LT 0.5 )
            temp2 = L * (1 + S);
        else
            temp2 = L + S - L * S;
        temp1 = 2 * L - temp2;

        Rtemp3 = H + 1/3;
        Gtemp3 = H;
        Btemp3 = H - 1/3;
        if ( Rtemp3 LT 0 )
            Rtemp3 = Rtemp3 + 1;
        if ( Gtemp3 LT 0 )
            Gtemp3 = Gtemp3 + 1;
        if ( Btemp3 LT 0 )
            Btemp3 = Btemp3 + 1;
        if ( Rtemp3 GT 1 )
            Rtemp3 = Rtemp3 - 1;    
        if ( Gtemp3 GT 1 )
            Gtemp3 = Gtemp3 - 1;    
        if ( Btemp3 GT 1 )
            Btemp3 = Btemp3 - 1;    
        
        if ( 6 * Rtemp3 LT 1 )
            R = temp1 + (temp2 - temp1) * 6 * Rtemp3;
        else
            if ( 2 * Rtemp3 LT 1 )
                R = temp2;
            else
                if ( 3 * Rtemp3 LT 2 )
                    R = temp1 + (temp2 - temp1) * ((2/3) - Rtemp3) * 6;
                else
                    R = temp1;
        
        if ( 6 * Gtemp3 LT 1 )
            G = temp1 + (temp2 - temp1) * 6 * Gtemp3;
        else
            if ( 2 * Gtemp3 LT 1 )
                G = temp2;
            else
                if ( 3 * Gtemp3 LT 2 )
                    G = temp1 + (temp2 - temp1) * ((2/3) - Gtemp3) * 6;
                else
                    G = temp1;
        
        if ( 6 * Btemp3 LT 1 )
            B = temp1 + (temp2 - temp1) * 6 * Btemp3;
        else
            if ( 2 * Btemp3 LT 1 )
                B = temp2;
            else
                if ( 3 * Btemp3 LT 2 )
                    B = temp1 + (temp2 - temp1) * ((2/3) - Btemp3) * 6;
                else
                    B = temp1;
    }
    Rhex = FormatBaseN(R*255,16);
    if ( Len(Rhex) EQ 1 )
        Rhex = "0" & Rhex;
    Ghex = FormatBaseN(G*255,16);
    if ( Len(Ghex) EQ 1 )
        Ghex = "0" & Ghex;
    Bhex = FormatBaseN(B*255,16);
    if ( Len(Bhex) EQ 1 )
        Bhex = "0" & Bhex;
    
    return UCase(Rhex & Ghex & Bhex);
}