JS function to calculate complementary colour?

Question

Does anybody know, off the top of your heads, a Javascript solution for calculating the complementary colour of a hex value?

There are a number of colour picking suites and palette generators on the web but I haven't seen any that actually calculate the colour dynamically using JS.

A detailed hint or a snippet would be very much appreciated.

Answer 1

Parsed through http://design.geckotribe.com/colorwheel/

    // Complement      temprgb={ r: 0, g: 0xff, b: 0xff }; // Cyan      temphsv=RGB2HSV(temprgb);      temphsv.hue=HueShift(temphsv.hue,180.0);      temprgb=HSV2RGB(temphsv);      console.log(temprgb); // Complement is red (0xff, 0, 0)            function RGB2HSV(rgb) {      	hsv = new Object();      	max=max3(rgb.r,rgb.g,rgb.b);      	dif=max-min3(rgb.r,rgb.g,rgb.b);      	hsv.saturation=(max==0.0)?0:(100*dif/max);      	if (hsv.saturation==0) hsv.hue=0;       	else if (rgb.r==max) hsv.hue=60.0*(rgb.g-rgb.b)/dif;      	else if (rgb.g==max) hsv.hue=120.0+60.0*(rgb.b-rgb.r)/dif;      	else if (rgb.b==max) hsv.hue=240.0+60.0*(rgb.r-rgb.g)/dif;      	if (hsv.hue<0.0) hsv.hue+=360.0;      	hsv.value=Math.round(max*100/255);      	hsv.hue=Math.round(hsv.hue);      	hsv.saturation=Math.round(hsv.saturation);      	return hsv;      }            // RGB2HSV and HSV2RGB are based on Color Match Remix [http://color.twysted.net/]      // which is based on or copied from ColorMatch 5K [http://colormatch.dk/]      function HSV2RGB(hsv) {      	var rgb=new Object();      	if (hsv.saturation==0) {      		rgb.r=rgb.g=rgb.b=Math.round(hsv.value*2.55);      	} else {      		hsv.hue/=60;      		hsv.saturation/=100;      		hsv.value/=100;      		i=Math.floor(hsv.hue);      		f=hsv.hue-i;      		p=hsv.value*(1-hsv.saturation);      		q=hsv.value*(1-hsv.saturation*f);      		t=hsv.value*(1-hsv.saturation*(1-f));      		switch(i) {      		case 0: rgb.r=hsv.value; rgb.g=t; rgb.b=p; break;      		case 1: rgb.r=q; rgb.g=hsv.value; rgb.b=p; break;      		case 2: rgb.r=p; rgb.g=hsv.value; rgb.b=t; break;      		case 3: rgb.r=p; rgb.g=q; rgb.b=hsv.value; break;      		case 4: rgb.r=t; rgb.g=p; rgb.b=hsv.value; break;      		default: rgb.r=hsv.value; rgb.g=p; rgb.b=q;      		}      		rgb.r=Math.round(rgb.r*255);      		rgb.g=Math.round(rgb.g*255);      		rgb.b=Math.round(rgb.b*255);      	}      	return rgb;      }        //Adding HueShift via Jacob (see comments)      function HueShift(h,s) {           h+=s; while (h>=360.0) h-=360.0; while (h<0.0) h+=360.0; return h;       }            //min max via Hairgami_Master (see comments)      function min3(a,b,c) {           return (a<b)?((a<c)?a:c):((b<c)?b:c);       }       function max3(a,b,c) {           return (a>b)?((a>c)?a:c):((b>c)?b:c);       }