Skip to content

Instantly share code, notes, and snippets.

@eyecatchup
Last active March 7, 2021 23:32
Show Gist options
  • Star 6 You must be signed in to star a gist
  • Fork 2 You must be signed in to fork a gist
  • Save eyecatchup/9536706 to your computer and use it in GitHub Desktop.
Save eyecatchup/9536706 to your computer and use it in GitHub Desktop.
HSV to RGB color conversion - JavaScript-Port from the excellent java algorithm by Eugene Vishnevsky at http://www.cs.rit.edu/~ncs/color/t_convert.html
/**
* HSV to RGB color conversion
*
* H runs from 0 to 360 degrees
* S and V run from 0 to 100
*
* Ported from the excellent java algorithm by Eugene Vishnevsky at:
* http://www.cs.rit.edu/~ncs/color/t_convert.html
*/
function hsvToRgb(h, s, v) {
var r, g, b;
var i;
var f, p, q, t;
// Make sure our arguments stay in-range
h = Math.max(0, Math.min(360, h));
s = Math.max(0, Math.min(100, s));
v = Math.max(0, Math.min(100, v));
// We accept saturation and value arguments from 0 to 100 because that's
// how Photoshop represents those values. Internally, however, the
// saturation and value are calculated from a range of 0 to 1. We make
// That conversion here.
s /= 100;
v /= 100;
if(s == 0) {
// Achromatic (grey)
r = g = b = v;
return [
Math.round(r * 255),
Math.round(g * 255),
Math.round(b * 255)
];
}
h /= 60; // sector 0 to 5
i = Math.floor(h);
f = h - i; // factorial part of h
p = v * (1 - s);
q = v * (1 - s * f);
t = v * (1 - s * (1 - f));
switch(i) {
case 0:
r = v;
g = t;
b = p;
break;
case 1:
r = q;
g = v;
b = p;
break;
case 2:
r = p;
g = v;
b = t;
break;
case 3:
r = p;
g = q;
b = v;
break;
case 4:
r = t;
g = p;
b = v;
break;
default: // case 5:
r = v;
g = p;
b = q;
}
return [
Math.round(r * 255),
Math.round(g * 255),
Math.round(b * 255)
];
}
@ninhxuanluu
Copy link

it's working perfectly, thank you so much!

@kaervin
Copy link

kaervin commented Apr 6, 2018

It's not perfect.
There is a case 6, which results in the same as case 0.
Without it the output of hsvToRgb(360, 100, 100) results in rgb(255,0,255), which is obviously wrong, as it should result in the same as hsvToRgb(0, 100, 100).
Look here: https://de.wikipedia.org/wiki/HSV-Farbraum (I know its in German, but the math should be universal)

@freuwoert
Copy link

It's not perfect.
There is a case 6, which results in the same as case 0.

Limiting "i" to a max of 5 should solve the problem. 😄

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment