[RESOLVED] preg_replace_callback help needed to get changed value only

[s0me0ne]

I'm trying to use preg_replace_callback, but I want it to replace the characters rather than give me back the original, plus the changed value

function inverse_hex($num_sent)
{
	$number = $num_sent[0];//found out this is an array

$number = hexdec($number);
$number = $number - 255;

if ($number < 0)
	$number *= -1;

$number = dechex($number);

$num_sent[0] = $number;

return $number;
}

$data = 'fzzz';
echo preg_replace_callback('/[A-Fa-f0-9]/s', 'inverse_hex', $data);

This code gives me
f0zzz
instead of
0zzz

😕

[nrg_alpha]

ok.. I slightly restructured things.. and in doing so, I get the result you have...

function inverse_hex($num_sent)
{
   $number = hexdec($num_sent[0]);
   $number = abs($number - 255);
   $number = dechex($number);
   $num_sent[0] = $number; // is $num_sent globalized? There is no passing by reference nor any global variable declaration within this function
   return $number; // at this point, $number = f0
}

$data = 'fzzz';
echo preg_replace_callback('/[a-f0-9]/is', 'inverse_hex', $data);

EDIT - Oops.. accidently removed something.. let me re-insert it:

The end result of $number is f0.. so what you are saying is that replace anything between a-f (case insensitive) or 0-9 with what is returned from the callback function... so your data string is fzzz.. only the f character is eiligable for a change, and it is replaced with f0, thus f0zzz..

What I am confused with is this $num_sent[0] business... there's nothing being passed into the function via a reference, nor are you declaring this variable as global within your function.. so I am at a loss as to what is happening there... (unless I am mssing something obvious).

What are you trying to accomplish?

[Weedpacket]

What he said. In terms of the function...

function inverse_hex($num_sent)
{
	$number = $num_sent[0];
// $number = 'f';
	$number = hexdec($number);
// $number = 15;
	$number = $number - 255;
// $number = 	-240;
	if ($number < 0)
		$number *= -1;
// $number = 240;	
	$number = dechex($number);
// $number = 'f0';	
	$num_sent[0] = $number; // Doesn't do anything

return $number;
}

What is the function supposed to do? Sure you don't mean "-15" rather than "-255"? For that matter, is that subtraction the right way around?

And if it's just a matter of changing single hex digits into single hex digits, then [man]strtr[/man] will achieve the same effect without needing a whole other function for it:

$data = strtr($data, '0123456789abcdefABCDEF','fedcba976543210543210');

for example.

[s0me0ne]

My whole point is to be able to convert any HTML hexadecimal strings in a XML or CSS file and inverse the colors.

It needs to be able to find #003 and then convert that to #ffc
or
if it finds #ffff00 then it should convert that to #0000ff

My regex in the first post doesnt do that, but I wasnt able to have it replace the things properly, because it still kept the old data, so I had to work with a simpler regex at first.

I cantuse a strtr() because it needs to find the possible regex
/(^{#){1,1}([A-Fa-f0-9]){3,} 6}/
and only then replace what it finds if there are 3 or 6 characters right after a #, although I still need to test to make sure if it finds 4 or 5 characters after the # to ignore that.

[Weedpacket]

s0me0ne wrote:

because it still kept the old data

No, it didn't - as doing more than one test would show. See nrg_alpha and my posts. The maths that you're having trouble with is still unnecessary: you can use strtr in the callback.

[nrg_alpha]

Fair enough.. examine the code below.. Let's pretend that the $str value is the results of doing a file_get_contents() on some silly nonsense CSS file...

$str = '#div_oopsContent {width: 700px; margin-top: 20px; margin-left: 33px; padding-top: 10px; border-top: 1px dashed #7489D0;}
.urlText {color: #98AEF7;}
.starSystem{width:22px;height:24px;float:left;background:url(/home/images/starSystem2-0.png) no-repeat 0 0;margin:0 0 5px 0}
a.firstStar{margin-left:10px}
a.goldStar{background-position:0 0;margin-right:1px}
a.emptyStar{background-position:-24px 0}
.homeDefList{width:200px;float:left;clear:both;padding-bottom:11px}
dt.dtimg img{float:left}dd{margin:-2px 0 0 11px}
.infoIcon,dd a{float:left}
.infoIcon{margin:-2px 3px 0 0}
.div_dropShadow{float:left;width:181px;height:97px;background-color:#2D3E9E;margin:5px 0 10px 16px}
#recentAdditionImage,#walkthroughImage{float:left;border:1px solid #000;margin:-5px 0 0 -5px}
#recentAdditionImage:hover,#walkthroughImage:hover{border:1px solid #FFF}';

function hexInverse($matches){
   $matches[1] = strtoupper($matches[1]);
   if(strlen($matches[1]) < 4){ // 3 character shorthand notation detected. Example: C30, which will be converted to CC3300
      $trans = array('0' => '00', '1' => '11', '2' => '22', '3' => '33', '4' => '44', '5' => '55', '6' => '66', '7' => '77', '8' => '88', '9' => '99',
		'A' => 'AA', 'B' => 'BB', 'C' => 'CC', 'D' => 'DD', 'E' => 'EE', 'F' => 'FF');
      $matches[1] = strtr($matches[1], $trans);
   }
   $invertRGB = array();
   $decToHex = NULL;
   for($t = 0, $x = 0; $t < 5; $t += 2){
      $invertRGB[$x] = 255 - (hexdec(substr($matches[1], $t, 2)));
      $decToHex .= (strlen(dechex($invertRGB[$x])) == 1)? '0'.dechex($invertRGB[$x]) : dechex($invertRGB[$x]);
      ++$x;
   }
   $decToHex = '#' . strtoupper($decToHex);
   return $decToHex;		
}

echo $str . '<br /><br />';
$str2 = preg_replace_callback('~(?:#([a-f0-9]{3,6}))~i', "hexInverse", $str);
echo $str2;

Output:

#div_oopsContent {width: 700px; margin-top: 20px; margin-left: 33px; padding-top: 10px; border-top: 1px dashed #7489D0;} .urlText {color: #98AEF7;} .starSystem{width:22px;height:24px;float:left;background:url(/home/images/starSystem2-0.png) no-repeat 0 0;margin:0 0 5px 0} a.firstStar{margin-left:10px} a.goldStar{background-position:0 0;margin-right:1px} a.emptyStar{background-position:-24px 0} .homeDefList{width:200px;float:left;clear:both;padding-bottom:11px} dt.dtimg img{float:left}dd{margin:-2px 0 0 11px} .infoIcon,dd a{float:left} .infoIcon{margin:-2px 3px 0 0} .div_dropShadow{float:left;width:181px;height:97px;background-color:#2D3E9E;margin:5px 0 10px 16px} #recentAdditionImage,#walkthroughImage{float:left;border:1px solid #000;margin:-5px 0 0 -5px} #recentAdditionImage:hover,#walkthroughImage:hover{border:1px solid #FFF}

#div_oopsContent {width: 700px; margin-top: 20px; margin-left: 33px; padding-top: 10px; border-top: 1px dashed #8B762F;} .urlText {color: #675108;} .starSystem{width:22px;height:24px;float:left;background:url(/home/images/starSystem2-0.png) no-repeat 0 0;margin:0 0 5px 0} a.firstStar{margin-left:10px} a.goldStar{background-position:0 0;margin-right:1px} a.emptyStar{background-position:-24px 0} .homeDefList{width:200px;float:left;clear:both;padding-bottom:11px} dt.dtimg img{float:left}dd{margin:-2px 0 0 11px} .infoIcon,dd a{float:left} .infoIcon{margin:-2px 3px 0 0} .div_dropShadow{float:left;width:181px;height:97px;background-color:#D2C161;margin:5px 0 10px 16px} #recentAdditionImage,#walkthroughImage{float:left;border:1px solid #FFFFFF;margin:-5px 0 0 -5px} #recentAdditionImage:hover,#walkthroughImage:hover{border:1px solid #000000}

Here is the breakdown in my thought process:

• I obviously plug $str into the preg_replace_callback, which inturn passes it to the hexInverse function.

• For every instance that preg pattern finds, I first convert all alpha characters to uppercase (just to keep things uniform).

• I then check to see if the match in question is less than 4 characters long (which denotes a shorthand version). And if so, using strtr, translate everything so that we go from say C30 to CC3300.

• Then I create a small sub loop that uses substr to access each pair of characters, convert to decimal and subtract that result from 255.

• Using $decToHex, I simply append each pair of the previous steps results as hex values once again.

• Lastly, I append the # character and once again convert all to uppcase for uniformity and return that value.

So did it work? If you look at the output, the first row is the "before" while the second is the "after".

If we take a look at the very first hex colour value we come across in the "before" row, we see #7489D0. If we follow the above steps:
in RGB terms, 74 = 116, 89 = 137, and D0 = 208.
therefore, to get the inverse:
255 - 116 = 139, 255 - 137 = 118, and 255 - 208 = 47
When I type in 139, 118,47 as the RGB values within the colour palette tool in photoshop, it shows me the hex value: #8B762F. Low and behold, this is the first value in the "after" row in the output.

[nrg_alpha]

One small slip up on my part.. while the last snippet works, while I was experimenting, I was using an array called $invertRGB within the function.. oops... this is not necessary... so the function could be as such instead:

function hexInverse($matches){
   $matches[1] = strtoupper($matches[1]);
   if(strlen($matches[1]) < 4){ // 3 character shorthand notation detected. Example: C30 = CC3300
      $trans = array('0' => '00', '1' => '11', '2' => '22', '3' => '33', '4' => '44', '5' => '55', '6' => '66', '7' => '77', '8' => '88', '9' => '99',
		'A' => 'AA', 'B' => 'BB', 'C' => 'CC', 'D' => 'DD', 'E' => 'EE', 'F' => 'FF');
      $matches[1] = strtr($matches[1], $trans);
   }
   $invertRGB = NULL;
   $decToHex = NULL;
   for($t = 0; $t < 5; $t += 2){
      $invertRGB = 255 - (hexdec(substr($matches[1], $t, 2)));
      $decToHex .= (strlen(dechex($invertRGB)) == 1)? '0'.dechex($invertRGB) : dechex($invertRGB);
   }
   $decToHex = '#' . strtoupper($decToHex);
   return $decToHex;		
}

It has no effect on the outcome, just removes an array and instead uses a regular variable (and gets ride of an extra variable within the for loop). My bad.

[Weedpacket]

The minor detail: that pattern back there ([0-9a-f]{3,6}) also accepts strings with 4 or 5 hex digits. You'll want b[/b] to restrict it to 3 or 6 - three and maybe three more.

But still ... so close ... but still too much hex arithmetic ...

function hexInverse($matches)
{
    $hexstring = strtolower($matches[1]);
    if(strlen($hexstring)==3)
    {
        $hexstring = $hexstring[0].$hexstring[0].$hexstring[1].$hexstring[1].$hexstring[2].$hexstring[2];
    }
    // Works because 15 (and 255, for that matter) is one less than a power of the base.
    $hexstring = strtr($hexstring,'0123456789abcdef','fedcba9876543210');
    return '#'.$hexstring;
}

Meanwhile .... there are other formats than hex strings for specifying colours in CSS. These won't be an issue?

[nrg_alpha]

Weedpacket;10898687 wrote:

The minor detail: that pattern back there ([0-9a-f]{3,6}) also accepts strings with 4 or 5 hex digits. You'll want b[/b] to restrict it to 3 or 6 - three and maybe three more.

In the wise words of Homer Simpson - 'D'oh!'
Good catch! I took the {3,6} for granted, but you are correct.. I should be more careful and make no assumptions... Perhaps one counter suggestion is to make the second set of parenthesis non-capturing:
([0-9a-f]{3}(?:[0-9a-f]{3})?), as I wouldn't imagine the need for a $matches[2] variable... unless I am missing something here.

Weedpacket;10898687 wrote:

But still ... so close ... but still too much hex arithmetic ...

function hexInverse($matches)
{
    $hexstring = strtolower($matches[1]);
    if(strlen($hexstring)==3)
    {
        $hexstring = $hexstring[0].$hexstring[0].$hexstring[1].$hexstring[1].$hexstring[2].$hexstring[2];
    }
    // Works because 15 (and 255, for that matter) is one less than a power of the base.
    $hexstring = strtr($hexstring,'0123456789abcdef','fedcba9876543210');
    return '#'.$hexstring;
}

Good god man! You know, now that I look at your code, it really sheds light on me over-thinking things... I feel so violated lol On a more serious note,
once again, you have proven a sleeker more efficient way of doing things (and I honestly thank you for it! I'm learning.. slowly but surely.....). This will really make me stand back, and see what other solutions are out there to ponder as opposed to more or less adopting what immediately comes to mind...

There's a saying along the lines of: 'Better to keep quite and look smart then to open your mouth and look stupid'. Everytime I put code suggestions, I run the risk of looking stupid, and well, we know how that turned out lol.. but in cases like this, I'd rather come forward and be corrected [look stupid] (yet walk away a notch wiser) than to 'say nothing' and not learn anything in return.

Weedpacket;10898687 wrote:

Meanwhile .... there are other formats than hex strings for specifying colours in CSS. These won't be an issue?

No doubt! If other notations creep up within say a CSS file, there would have to be some additions to be made to accomodate them. Since the OP mentioned hex values, I figured I would stick to that.. but yes, you are correct again, sir.

[s0me0ne]

Thanks. I'm always amazed by everyone's more efficient methods than i could ever come up with.