RGB to HSV color in javascript? [closed]

Answer 1

Pure JS, shortest

Try this (more: hsv2rgb, rgb2hsl, hsl2rgb and sl22sv):

// input: r,g,b in [0,1], out: h in [0,360) and s,v in [0,1]
function rgb2hsv(r,g,b) {
  let v=Math.max(r,g,b), c=v-Math.min(r,g,b);
  let h= c && ((v==r) ? (g-b)/c : ((v==g) ? 2+(b-r)/c : 4+(r-g)/c)); 
  return [60*(h<0?h+6:h), v&&c/v, v];
}

function rgb2hsv(r,g,b) {
  let v=Math.max(r,g,b), c=v-Math.min(r,g,b);
  let h= c && ((v==r) ? (g-b)/c : ((v==g) ? 2+(b-r)/c : 4+(r-g)/c)); 
  return [60*(h<0?h+6:h), v&&c/v, v];
}

console.log(`rgb: (0.5,0.2,0.3) --> hsv: (${rgb2hsv(0.5,0.2,0.3)})`)


// ---------------
// UX
// ---------------

rgb= [0,0,0];
hs= [0,0,0];

let $ = x => document.querySelector(x);
let c = (x,s) => $(x).style.backgroundColor=s;

let hsv2rgb = (h,s,v, f= (n,k=(n+h/60)%6) => v - v*s*Math.max( Math.min(k,4-k,1), 0)) => [f(5),f(3),f(1)];    

function changeRGB(i,e) {
  rgb[i]=e.target.value/255;
  hs = rgb2hsv(...rgb);
  refresh();
}

function changeHS(i,e) {
  hs[i]=e.target.value/(i?255:1);
  rgb= hsv2rgb(...hs);
  refresh();
}

function refresh() {
  rr = rgb.map(x=>x*255|0).join(', ')
  tr = `RGB: ${rr}`
  th = `HSV: ${hs.map((x,i)=>i? (x*100).toFixed(2)+'%':x|0).join(', ')}`
  $('.box').style.backgroundColor=`rgb(${rr})`;  
  $('.infoRGB').innerHTML=`${tr}`;  
  $('.infoHS').innerHTML =`${th}`;  
  
  $('#r').value=rgb[0]*255;
  $('#g').value=rgb[1]*255;
  $('#b').value=rgb[2]*255;
  
  $('#h').value=hs[0];
  $('#s').value=hs[1]*255;
  $('#v').value=hs[2]*255;  
}

refresh();

.box {
  width: 50px;
  height: 50px;
  margin: 20px;
}

body {
    display: flex;
}

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This based on this formulas wiki - I made error analysis to show that results are correct