mpbzh / php-rgb-hsl-converter Goto Github PK

In Line 99 $s is calculated like this:
$s = 1 - abs(2 * $l - 1);
According to Wikipedia S is calculated be dividing Chroma by the therm above. For me changing the line to
$s = $chroma / (1 - abs(2 * $l - 1));

worked out. May somebody can verify this and if it is correct change it for the others.
Thank you in advance and nice software!

Thank you for this marvelous piece of software!
While converting the 141 browser colors, I found that s didn't agree with the results on
http://colorizer.org/ and that they didn't quite look like the hex colors.
It turned out to be the value of s isn't computed correctly for all cases.
https://en.wikipedia.org/wiki/HSL_and_HSV#Converting_to_RGB
Here's the change I made (including the debugging code.)
186 $h = $h_ / 6;
187 //echo(LINE.' $h='.$h.".\n ");
188 //*********************************************************************
189 // https://en.wikipedia.org/wiki/HSL_and_HSV#Converting_to_RGB ***
190 // Adjustment needed to compute correct value of $s (saturation). ***
191 //*********************************************************************
192 if ($l < 0.5) {
193 $s = ($max-$min)/($max+$min);
194 //echo(LINE.' $s='.$s.".\n");
195 } else {
196 $s = ($max-$min)/(2.0-$max-$min);
198 //echo(LINE.' $s='.$s.".\n");
199 }
The Wikipedia article computes it one way for l < 0.5 and another for l > 0.5.
Nothing for l == 5...artists!

With this small addition, the function returns exactly what colorizer.org does.

I converted cc0000 into hsl then back to hex and the color returned wasn't cc0000. Same thing happened for 003366. It seems like some colors work, but others do not. Maybe a rounding issue?