Question

I need a way in PHP/HTML to generate a list from 1 to 100 of colors (hex codes). Zero is red, and 100 is green, and each in-between is a shade that smoothly flows between the two. (for example, red to orange to yellow to green).

So say I can throw a number at it, like the number 50, and it returns a hexadecimal code from the list (50 would be yellow).

Is the only way to manually assign each color in an array? Or is there some easier method?

_{This request is quite odd – I’ve searched around, but I can’t find anything like it.}

Answer 1

Give this a try:

function rgb($val){
  if($val < 0 || $val > 100)
    return; // Error!

  $r = (100 - $val)*255/50;
  if((100 - $val) > 50)
    $r = 255;
  $rr = dechex($r);
  if($r < 16)
    $rr = '0' . $rr;

  $g = ($val)*255/50;
  if((100-$val) < 50)
    $g = 255;
  $gg = dechex($g);
  if($g < 16)
    $gg = '0'.$gg;

  $bb = '00';

  return $rr . $gg . $bb;
}

Here are the output values from 0-100 going by 10’s:

ff0000
ff3300
ff6600
ff9900
ffcc00
ffff00
ccff00
99ff00
66ff00
33ff00
00ff00