JS function to calculate complementary colour?
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); }
I find that taking the bit-wise complement works well, and quickly.
var color = 0x320ae3;var complement = 0xffffff ^ color;I'm not sure if it's a perfect complement in the sense of "mixes together to form a 70% grey", however a 70% grey is "pure white" in terms of color timing in film. It occurred to me that XORing the RGB hex out of pure white might be a good first approximation. You could also try a darker grey to see how that works for you.
Again, this is a fast approximation and I make no guarantees that it'll be perfectly accurate.
See https://github.com/alfl/textful/blob/master/app.js#L38 for my implementation.
None of the other functions here worked out the box, so I made this one.
It takes a hex value, converts it to HSL, shifts the hue 180 degrees and converts back to Hex
/* hexToComplimentary : Converts hex value to HSL, shifts * hue by 180 degrees and then converts hex, giving complimentary color * as a hex value * @param [String] hex : hex value * @return [String] : complimentary color as hex value */function hexToComplimentary(hex){ // Convert hex to rgb // Credit to Denis http://stackoverflow.com/a/36253499/4939630 var rgb = 'rgb(' + (hex = hex.replace('#', '')).match(new RegExp('(.{' + hex.length/3 + '})', 'g')).map(function(l) { return parseInt(hex.length%2 ? l+l : l, 16); }).join(',') + ')'; // Get array of RGB values rgb = rgb.replace(/[^\d,]/g, '').split(','); var r = rgb[0], g = rgb[1], b = rgb[2]; // Convert RGB to HSL // Adapted from answer by 0x000f http://stackoverflow.com/a/34946092/4939630 r /= 255.0; g /= 255.0; b /= 255.0; var max = Math.max(r, g, b); var min = Math.min(r, g, b); var h, s, l = (max + min) / 2.0; if(max == min) { h = s = 0; //achromatic } else { var d = max - min; s = (l > 0.5 ? d / (2.0 - max - min) : d / (max + min)); if(max == r && g >= b) { h = 1.0472 * (g - b) / d ; } else if(max == r && g < b) { h = 1.0472 * (g - b) / d + 6.2832; } else if(max == g) { h = 1.0472 * (b - r) / d + 2.0944; } else if(max == b) { h = 1.0472 * (r - g) / d + 4.1888; } } h = h / 6.2832 * 360.0 + 0; // Shift hue to opposite side of wheel and convert to [0-1] value h+= 180; if (h > 360) { h -= 360; } h /= 360; // Convert h s and l values into r g and b values // Adapted from answer by Mohsen http://stackoverflow.com/a/9493060/4939630 if(s === 0){ r = g = b = l; // achromatic } else { var hue2rgb = function hue2rgb(p, q, t){ if(t < 0) t += 1; if(t > 1) t -= 1; if(t < 1/6) return p + (q - p) * 6 * t; if(t < 1/2) return q; if(t < 2/3) return p + (q - p) * (2/3 - t) * 6; return p; }; var q = l < 0.5 ? l * (1 + s) : l + s - l * s; var p = 2 * l - q; r = hue2rgb(p, q, h + 1/3); g = hue2rgb(p, q, h); b = hue2rgb(p, q, h - 1/3); } r = Math.round(r * 255); g = Math.round(g * 255); b = Math.round(b * 255); // Convert r b and g values to hex rgb = b | (g << 8) | (r << 16); return "#" + (0x1000000 | rgb).toString(16).substring(1);}