javascript - Interpolate HSL Colours -

i building star visualisation engine, , need interpolate values received api. hsl colour stops are:

-.63, hsl: 228° 100% 80%, .165, hsl: 224° 100% 90%, .33, hsl: 240° 100% 98%, .495, hsl: 64° 100% 92%, .66, hsl: 52° 100% 82%, .825, hsl: 28° 100% 66%, 2.057, hsl: 6° 95% 65%, 

each star return colour value between -.63 , 2.057, need function takes value , gets colour along spectrum comprised of above stops.

i've had previous cannot life of me figure out, , haven't been able find concise tutorial or walkthrough of interpolating hsl values. way can figure out via external lib, seems ridiculous solution relatively simple. appreciated!

a straightforward linear interpolation function in hsb space:

function get_color_for(value) {     var i, h,s,b,stops = [         [-0.63, [228, 100, 80]],         [0.165, [224, 100, 90]],         [0.33, [240, 100, 98]],         [0.495, [64, 100, 92]],         [0.66, [52, 100, 82]],         [0.825, [28, 100, 66]],         [2.057, [6, 95, 65]]     ];     if (value <= stops[0][0]) return stops[0][1];     if (value >= stops[stops.length - 1][0]) return stops[stops.length - 1][1];     = 0;     while (value > stops[i][0])        i++;     value -= stops[i-1][0];     value /= (stops[i][0]-stops[i-1][0]);     h = stops[i-1][1][0]+(stops[i][1][0]-stops[i-1][1][0])*value;     s = stops[i-1][1][1]+(stops[i][1][1]-stops[i-1][1][1])*value;     b = stops[i-1][1][2]+(stops[i][1][2]-stops[i-1][1][2])*value;     return [h,s,b]; } 

for values lower minimum input return first, , higher maximum, last color set.

the returned value hsl array, can used in css. if environment needs rgb colors can use hsl-to-rgb conversion function, such in this earlier question. check output device expects rgb range: 0.0 1.0, 0 100, or 0 255.

note function cannot used hsb in general. problem hue part: wraps around @ 360 (degrees), , attempting interpolate between 350 , 10 make return cyan (the value around 170) instead of red (the value @ 0).

here jsfiddle, displaying output range of numbers.