Opposite Hex Color Code

dngzone

Looking around to find possible code to figure out the HEX color opposite of a particular inputted color using PHP. If anyone has any ideas or code on how to do this, please let me know!

diego25

How do you define "opposite"?

Diego

feldon23

Add 128 (80 in Hex) to each of the 3 numbers.

If they wrap around past 255 (FF), subtract 255 (FF).

Weedpacket

I'm not sure if "the opposite" would be equivalent to adding 128 to each component - that would make black come out mid-grey, and white into a grey one tick darker. I think you mean to subtract each component from 255.

Does the string $hex have the # still attached, or not?
If so, a str_replace will get rid of it for the moment.

$rgb = hexdec($hex);
$rgb ^= 0xffffff;
$hex = substr('000000'.dechex($rgb), -6);

and then put the # back on the beginning again.

OR:

$hex = strtr('0123456789ABCDEF', 'FEDCBA9876543210', strtoupper($hex));

'course, if you do want to add 0x80 and wrap;

$rgb = hexdec($hex);
$red = ((($rgb>>16)&0xff)+0x80)&0xff;
$green = ((($rgb>>8)&0xff)+0x80)&0xff;
$blue = (($rgb&0xff)+0x80)&0xff;
$hex = sprintf('%02X%02X%02X', $red, $green, $blue);

$hex = $hex{0} . strtr('0123456789ABCDEF', 'FEDCBA9876543210', strtoupper($hex{1}))
       $hex{2} . strtr('0123456789ABCDEF', 'FEDCBA9876543210', strtoupper($hex{3}))
       $hex{4} . strtr('0123456789ABCDEF', 'FEDCBA9876543210', strtoupper($hex{5}));

There are of course other ways to do either task.

dngzone

to Weedpacket!

That works perfect!... Just what I was looking for....
Thanks for the code examples!

Here's my example:

<?
$init_clr = "21008C";
$rgb = hexdec($init_clr);
$rgb ^= 0xffffff;
$hex = substr('000000'.dechex($rgb), -6);
?>
<center>
<table width="50%">
<tr>
<td bgcolor="#<?=$init_clr;?>">
<br><br><br><br>
</td>
<td bgcolor="#<?=$hex;?>">
<br><br><br><br>
</td>
</tr>
</table>