Convert wavelength in nm to RGB
Maybe some day you'll need to convert wavelengthes in nanometers to RGB values.I just needed it for visualizing emission values of flourescent dyes in a lab information system.
I didn't want to make that by hand, picking e.g. 20 values from the color range to let them stand for everything between them, but wanted to have a proper and (at least approximately) exact solution.
The function below is based on an algorithm developed by Dan Bruton I found in the web.
I just transcribed it to PHP, and it works pretty good.
<?php
function wavtorgb($w){
$w = intval($w);
if(!$w) return false;
//color
if($w >= 100 AND $w < 380){
$r = 0.91;
$g = 0.77;
$b = 1.0;
}elseif($w >= 380 AND $w < 440){
$r = abs($w - 440) / (440 - 350);
$g = 0.0;
$b = 1.0;
}elseif($w >= 440 AND $w < 490){
$r = 0.0;
$g = abs($w - 440) / (490 - 440);
$b = 1.0;
}elseif($w >= 490 AND $w < 510){
$r = 0.0;
$g = 1.0;
$b = abs($w - 510) / (510 - 490);
}elseif($w >= 510 AND $w < 580){
$r = abs($w - 510) / (580 - 510);
$g = 1.0;
$b = 0.0;
}elseif($w >= 580 AND $w < 645){
$r = 1.0;
$g = abs($w - 645) / (645 - 580);
$b = 0.0;
}elseif($w >= 645 AND $w < 780){
$r = 1.0;
$g = 0.0;
$g = 0.0;
}elseif($w >= 780 AND $w < 1000000){
$r = 1.0;
$g = 0.31;
$b = 0.31;
}else{
$r = 0.0;
$g = 0.0;
$b = 0.0;
}
//let the intensity sss fall off near the vision limits
if($w >= 380 AND $w < 420){
$sss = 0.3 + 0.7*($w - 350) / (420 - 350);
}elseif($w >= 420 AND $w <= 700){
$sss = 1.0;
}elseif($w > 700 AND $w <= 780){
$sss = 0.3 + 0.7*(780 - $w) / (780 - 700);
}else{
$sss = 1.0;
}
$sss *= 255;
$r = intval($sss * $r);
$g = intval($sss * $g);
$b = intval($sss * $b);
//label
if($w >= 100 AND $w < 380){
$label = $w."nm (UV)";
}elseif($w >= 380 AND $w < 780){
$label = $w."nm";
}elseif($w >= 780 AND $w < 1000000){
$label = $w."nm (IR)";
}else{
return false;
}
$return = array($r, $g, $b, $label);
return $return;
}
?>
