JavaScript: image average color

average-color.js

var getAverageColor = (function(window, document, undefined){
	return function(imageURL, options}){
		options = {
			// image split into blocks of x pixels wide, 1 high
			blocksize: options.blocksize || 5,
			fallbackColor: options.fallbackColor || '#000'
		};

		var img = document.createElement('img'),
			canvas = document.createElement('canvas'),
			context = canvas.getContext && canvas.getContext('2d'),
			i = -4,
			count = 0,
			rgb = {
				r: 0,
				g: 0,
				b: 0
			},
			data, width, height, length;

		if(!context){
			return options.fallback_color;
		}

		height = canvas.height = img.naturalHeight || img.offsetHeight || img.height;
		width = canvas.width = img.naturalWidth || img.offsetWidth || img.width;

		// create a dom element for the image
		img.src = imageURL;
		img.id = 'averageColorImg';
		img.style.display = 'none';

		// draw image in canvas to make calculation easier
		context.drawImage(img, 0, 0);

		try {
			data = context.getImageData(0, 0, width, height);
		}
		catch(e){
			// security error, img on different domain
			return options.fallback_color;
		}

		length = data.data.length;

		// get rgb values for each pixel at the end of the block
		while((i += blocksize * 4) < length){
			++count;
			rgb.r += data.data[i];
			rgb.g += data.data[i+1];
			rgb.b += data.data[i+2];
		}

		// ~~used to floor values
		rgb.r = ~~(rgb.r/count);
		rgb.g = ~~(rgb.g/count);
		rgb.b = ~~(rgb.b/count);

		return 'rgb('+rgb.r+', '+rgb.g+', '+rgb.b+')';
	};
})(this, this.document);

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// complement color
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
temprgb=thisrgb;
temphsv=RGB2HSV(temprgb);
temphsv.hue=HueShift(temphsv.hue,180.0);
temprgb=HSV2RGB(temphsv);

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); 
}