how to generate unique hexcolors?

[PHPycho]

Hello forums!
I am getting problem in generating unique hexcolors ie ##*$!#*$!
Can anybody provide me the help regarding generation of unique hexcolors?
Thanks to all of You in advance..

[mcavic]

What do you mean by unique?

[PHPycho]

Unique means:
Each time the generated color should be unique to the previous one..
Anyway thanks for the reply

[whoisgregg]

What does your random hex color generator code look like so far? :)

[mooger35]

do you have to use hex colors?

what about using rgb format? Then just randomize three numbers between 0 and 255?

example

rgb(230, 232, 250) would give you silver.

[whoisgregg]

Here's a little function to spit out as many unique hex colors as you need. Note it doesn't care how similar the colors are, only that they are unique. So, you could end up with FFFFFF, FFFFFE, FFFFFD, etc.

Try not to generate more than a thousand or so. Each new color needs to be compared to all previous colors so the processing time increases exponentially. Maybe quadratically? Or factorially? I don't know, it just gets slower and slower. ;)

<?php
function generateUniqueHexColors($quantity=10){
if($quantity >= (254*254*254)){ // Don't try to generate the full set of hex colors this way.
return false;
}
$colors = array();
$quantity = (intval($quantity) == 0)? 1 : intval($quantity);
for($i=0; $i<$quantity; $i++){
$color = sprintf("%02X%02X%02X", mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));
while( in_array($color, $colors) ){
//echo $i.': '.$color.' already existed<br />'; // uncomment to debug
$color = sprintf("%02X%02X%02X", mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));
}
$colors[] = $color;
}
return $colors;
}
$colors = generateUniqueHexColors(1000); // anything over 1000 is rather slow
/*/ To test that it worked:
$unique = array_unique($colors);
if( $colors!= $unique ){ echo '<h1>Failed!</h1>'; } else { echo '<h1>Success!</h1>'; }
print_r($colors);
// */
echo '<style type="text/css">div.b { width: 20px; height: 20px; float:left; }</style>';
foreach($colors as $c=>$v){
echo '<div style="background-color: #'.$v.'" class="b"></div>';
}
?>