I am trying to determine colors for my site's themes. A great way I've found to do so is to take a main 6-digit hex color and simply add opacity on to the end of the hex code to get a complimentary color. The problem I'm having is that any time the secondary (the 8-digit hex code) color is to be on top of the main color you can't see it. Is there any way in css or php to convert an 8-digit hex code to it's equivalent color in a normal 6-digit hex code.
For example, my main color and secondary colors are as follows:
#053d06
#053d0614
I could go into a color picker and grab the secondary color and manually code it that way, but I'm trying to do it programmatically. I have tried clemblanco's rgba2hex/hex2rgba code, but that seems to just translate it back to the main color instead of the equivalent secondary color. Any help is appreciated! Thank you.
ETA: More directly I want a hex color that is the same color as the 8-digit code put over a white background. Thank you.
Directly getting the substring or dividing off the two hex digits 16**2 -> 256 could be a practical way to truncate 'em if that's all you're after
php > $hex = "#053d0614";
php > echo substr($hex, 0, 7);
#053d06
php > echo '#'.substr('000000'.dechex(intdiv(hexdec($hex), 256)), -6);
#053d06
SOLUTION: I ended up just adjusting the brightness of my main color instead of trying to convert an alpha hex to a non-alpha hex. Here is what I am using and it works great:
function adjustBrightness($hexCode, $adjustPercent) {
$hexCode = ltrim($hexCode, '#');
if (strlen($hexCode) == 3) {
$hexCode = $hexCode[0] . $hexCode[0] . $hexCode[1] . $hexCode[1] . $hexCode[2] . $hexCode[2];
}
$hexCode = array_map('hexdec', str_split($hexCode, 2));
foreach ($hexCode as & $color) {
$adjustableLimit = $adjustPercent < 0 ? $color : 255 - $color;
$adjustAmount = ceil($adjustableLimit * $adjustPercent);
$color = str_pad(dechex($color + $adjustAmount), 2, '0', STR_PAD_LEFT);
}
return '#' . implode($hexCode);
}
I'm facing this situation where I have an ID which comes from a database (so it can be 1, 100, 1000, ...) and I need to generate random colors, however equal ID's should result in the same color.
Any suggestion on how I can achieve this?
Thanks!
Use a cryptographic hash and clip the bytes you don't need:
function getColor($num) {
$hash = md5('color' . $num); // modify 'color' to get a different palette
return array(
hexdec(substr($hash, 0, 2)), // r
hexdec(substr($hash, 2, 2)), // g
hexdec(substr($hash, 4, 2))); //b
}
The resulting (code to generate it) looks like this for the numbers 0-20:
<?php
// someting like this?
$randomString = md5($your_id_here); // like "d73a6ef90dc6a ..."
$r = substr($randomString,0,2); //1. and 2.
$g = substr($randomString,2,2); //3. and 4.
$b = substr($randomString,4,2); //5. and 6.
?>
<style>
#topbar { border-bottom:4px solid #<?php echo $r.$g.$b; ?>; }
</style>
The obvious approach is to just convert the ID into a color (e.g. lower 8 bits are the blue, next 8 bits are Green, next 8 are Red - leave 8 bits, but I'm sure you can figure that out ;-)
Assuming this doesn't work (cos you end up with a horrible color palette:
Use an array (or hash table) to make a mapping of IDs to Colors.
If you are concerned that there are too many IDs, then you could apply some hash to the ID and use that as you key into the "id to color" mapping. In this case you are effectively saying one id always has one color, but one color can be used by many IDs.
If the array is always sorted, you can use this algorythm up to 250 items:
<?php
function getRGBColorString( $array )
{
$indexColor = round( 250 / count( $array ) );
$iterator = 1;
$arrayOfRGB = array();
foreach( $array as $item)
{
$arrayOfRGB[] = "rgb(" . ( $indexColor * $iterator ) . ", 113, 113 )";
$iterator++;
}
return $arrayOfRGB;
}
?>
I want to generate a unique 4-6 char long AlphaNumeric string to save in db with each record(user). The db field has a unique index, so trying to save a pre-existing string generates an error. Right now I am generating a random string and using try-catch, so when adding a new record if it throws an exception, I generate another random string and attempt to save again, and the code keep trying until it adds a record successfully. This whole solution not only looks heavy but also ugly, so I want to change it. I am interested in an elegant solution, so any help/guidance is welcome.
With the given information :
id must be unique
id must not be numeric
id must not represent a sequential series
id will not be input by the user
The PHP function uniqid is exactly what you need. Though it returns a 13 character long hexadecimal value.
** Edit **
Yes, uniqid will return a seamingly sequential number, but we can get around this easily. Consider this code
class IDGenerator {
//const BIT_MASK = '01110011';
static public function generate() {
$id = uniqid();
$id = base_convert($id, 16, 2);
$id = str_pad($id, strlen($id) + (8 - (strlen($id) % 8)), '0', STR_PAD_LEFT);
$chunks = str_split($id, 8);
//$mask = (int) base_convert(IDGenerator::BIT_MASK, 2, 10);
$id = array();
foreach ($chunks as $key => $chunk) {
//$chunk = str_pad(base_convert(base_convert($chunk, 2, 10) ^ $mask, 10, 2), 8, '0', STR_PAD_LEFT);
if ($key & 1) { // odd
array_unshift($id, $chunk);
} else { // even
array_push($id, $chunk);
}
}
return base_convert(implode($id), 2, 36);
}
}
echo IDGenerator::generate();
Which will give results like
ivpa493xrx7
d173barerui
evpoiyjdryd
99ej19mnau2
Since there is nothing added or modified, except shuffling the bits around, there should not be any duplicated values and everything seems random. Voilà!
** Update (2014-02-24) **
I update this piece of code since the time it was originally posted. You may find the revised version here
I use the following method to pad out a ID for a property on our website:
function generateAgentRef($id,$length=5,$strPrefix='1'){
return $strPrefix . str_pad($id,$length,0,0);
}
Basically it will prefix 1 and then pad out the id with 0's until the string reaches $length.
But, I now have a requirement to revert this process. For example if I have the following IDs: 100650,100359,100651,100622,100112,100687, how can I get the ID e.g. 650, 359, 651, 622, 112, 687?
Hope this explains what I'm trying to achieve.
The ID in the database will never start with 0, so I was thinking of iterating over the components of the string and detecting when I hit something other than 0 and then splitting the string.
substract 100000 from the generated ref and intval() it could work if the length is 6 numbers exactly.
try using this
$a = substr($num,3);
here $num is the id you get
$a will be your desired number i.e 100659 shortened to 659
Expanding on your initial function
function getAgentId($id, $length = 5, $strPrefix = 1){
return $id - generateAgentRef(0, $length, $strPrefix);
}
$id = generateAgentRef(255);
echo $id, PHP_EOL; // 100255
echo getAgentId($id), PHP_EOL; //255
I want to create a unique id but uniqid() is giving something like '492607b0ee414'. What i would like is something similar to what tinyurl gives: '64k8ra'. The shorter, the better. The only requirements are that it should not have an obvious order and that it should look prettier than a seemingly random sequence of numbers. Letters are preferred over numbers and ideally it would not be mixed case. As the number of entries will not be that many (up to 10000 or so) the risk of collision isn't a huge factor.
Any suggestions appreciated.
Make a small function that returns random letters for a given length:
<?php
function generate_random_letters($length) {
$random = '';
for ($i = 0; $i < $length; $i++) {
$random .= chr(rand(ord('a'), ord('z')));
}
return $random;
}
Then you'll want to call that until it's unique, in pseudo-code depending on where you'd store that information:
do {
$unique = generate_random_letters(6);
} while (is_in_table($unique));
add_to_table($unique);
You might also want to make sure the letters do not form a word in a dictionnary. May it be the whole english dictionnary or just a bad-word dictionnary to avoid things a customer would find of bad-taste.
EDIT: I would also add this only make sense if, as you intend to use it, it's not for a big amount of items because this could get pretty slow the more collisions you get (getting an ID already in the table). Of course, you'll want an indexed table and you'll want to tweak the number of letters in the ID to avoid collision. In this case, with 6 letters, you'd have 26^6 = 308915776 possible unique IDs (minus bad words) which should be enough for your need of 10000.
EDIT:
If you want a combinations of letters and numbers you can use the following code:
$random .= rand(0, 1) ? rand(0, 9) : chr(rand(ord('a'), ord('z')));
#gen_uuid() by gord.
preg_replace got some nasty utf-8 problems, which causes the uid somtimes to contain "+" or "/".
To get around this, you have to explicitly make the pattern utf-8
function gen_uuid($len=8) {
$hex = md5("yourSaltHere" . uniqid("", true));
$pack = pack('H*', $hex);
$tmp = base64_encode($pack);
$uid = preg_replace("#(*UTF8)[^A-Za-z0-9]#", "", $tmp);
$len = max(4, min(128, $len));
while (strlen($uid) < $len)
$uid .= gen_uuid(22);
return substr($uid, 0, $len);
}
Took me quite a while to find that, perhaps it's saves somebody else a headache
You can achieve that with less code:
function gen_uid($l=10){
return substr(str_shuffle("0123456789abcdefghijklmnopqrstuvwxyz"), 0, $l);
}
Result (examples):
cjnp56brdy
9d5uv84zfa
ih162lryez
ri4ocf6tkj
xj04s83egi
There are two ways to obtain a reliably unique ID: Make it so long and variable that the chances of a collision are spectacularly small (as with a GUID) or store all generated IDs in a table for lookup (either in memory or in a DB or a file) to verify uniqueness upon generation.
If you're really asking how you can generate such a short key and guarantee its uniqueness without some kind of duplicate check, the answer is, you can't.
Here's the routine I use for random base62s of any length...
Calling gen_uuid() returns strings like WJX0u0jV, E9EMaZ3P etc.
By default this returns 8 digits, hence a space of 64^8 or roughly 10^14,
this is often enough to make collisions quite rare.
For a larger or smaller string, pass in $len as desired. No limit in length, as I append until satisfied [up to safety limit of 128 chars, which can be removed].
Note, use a random salt inside the md5 [or sha1 if you prefer], so it cant easily be reverse-engineered.
I didn't find any reliable base62 conversions on the web, hence this approach of stripping chars from the base64 result.
Use freely under BSD licence,
enjoy,
gord
function gen_uuid($len=8)
{
$hex = md5("your_random_salt_here_31415" . uniqid("", true));
$pack = pack('H*', $hex);
$uid = base64_encode($pack); // max 22 chars
$uid = ereg_replace("[^A-Za-z0-9]", "", $uid); // mixed case
//$uid = ereg_replace("[^A-Z0-9]", "", strtoupper($uid)); // uppercase only
if ($len<4)
$len=4;
if ($len>128)
$len=128; // prevent silliness, can remove
while (strlen($uid)<$len)
$uid = $uid . gen_uuid(22); // append until length achieved
return substr($uid, 0, $len);
}
Really simple solution:
Make the unique ID with:
$id = 100;
base_convert($id, 10, 36);
Get the original value again:
intval($str,36);
Can't take credit for this as it's from another stack overflow page, but I thought the solution was so elegant and awesome that it was worth copying over to this thread for people referencing this.
You could use the Id and just convert it to base-36 number if you want to convert it back and forth. Can be used for any table with an integer id.
function toUId($baseId, $multiplier = 1) {
return base_convert($baseId * $multiplier, 10, 36);
}
function fromUId($uid, $multiplier = 1) {
return (int) base_convert($uid, 36, 10) / $multiplier;
}
echo toUId(10000, 11111);
1u5h0w
echo fromUId('1u5h0w', 11111);
10000
Smart people can probably figure it out with enough id examples. Dont let this obscurity replace security.
I came up with what I think is a pretty cool solution doing this without a uniqueness check. I thought I'd share for any future visitors.
A counter is a really easy way to guarantee uniqueness or if you're using a database a primary key also guarantees uniqueness. The problem is it looks bad and and might be vulnerable. So I took the sequence and jumbled it up with a cipher. Since the cipher can be reversed, I know each id is unique while still appearing random.
It's python not php, but I uploaded the code here:
https://github.com/adecker89/Tiny-Unique-Identifiers
Letters are pretty, digits are ugly.
You want random strings, but don't want "ugly" random strings?
Create a random number and print it in alpha-style (base-26), like the reservation "numbers" that airlines give.
There's no general-purpose base conversion functions built into PHP, as far as I know, so you'd need to code that bit yourself.
Another alternative: use uniqid() and get rid of the digits.
function strip_digits_from_string($string) {
return preg_replace('/[0-9]/', '', $string);
}
Or replace them with letters:
function replace_digits_with_letters($string) {
return strtr($string, '0123456789', 'abcdefghij');
}
You can also do it like tihs:
public static function generateCode($length = 6)
{
$az = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$azr = rand(0, 51);
$azs = substr($az, $azr, 10);
$stamp = hash('sha256', time());
$mt = hash('sha256', mt_rand(5, 20));
$alpha = hash('sha256', $azs);
$hash = str_shuffle($stamp . $mt . $alpha);
$code = ucfirst(substr($hash, $azr, $length));
return $code;
}
You can do that without unclean/costy stuff like loops, String concatenations or multiple calls to rand(), in a clean and easy to read way. Also, it is better to use mt_rand():
function createRandomString($length)
{
$random = mt_rand(0, (1 << ($length << 2)) - 1);
return dechex($random);
}
If you need the String to have the exact length in any case, just pad the hex number with zeros:
function createRandomString($length)
{
$random = mt_rand(0, (1 << ($length << 2)) - 1);
$number = dechex($random);
return str_pad($number, $length, '0', STR_PAD_LEFT);
}
The "theoretical backdraw" is, that you are limited to PHPs capabilities - but this is more a philosophical issue in that case ;) Let's go through it anyways:
PHP is limited in what it can represent as a hex number doing it like this. This would be $length <= 8 at least on a 32bit system, where PHPs limitation for this should be 4.294.967.295 .
PHPs random number generator also has a maximum. For mt_rand() at least on a 32bit system, it should be 2.147.483.647
So you are theoretically limited to 2.147.483.647 IDs.
Coming back to the topic - the intuitive do { (generate ID) } while { (id is not uniqe) } (insert id) has one drawback and one possible flaw that might drive you straight to darkness...
Drawback: The validation is pessimistic. Doing it like this always requires a check at the database. Having enough keyspace (for example length of 5 for your 10k entries) will quite unlikely cause collisions as often, as it might be comparably less resource consuming to just try to store the data and retry only in case of a UNIQUE KEY error.
Flaw: User A retrieves an ID that gets verified as not taken yet. Then the code will try to insert the data. But in the meantime, User B entered the same loop and unfortunately retrieves the same random number, because User A is not stored yet and this ID was still free. Now the system stores either User B or User A, and when attempting to store the second User, there already is the other one in the meantime - having the same ID.
You would need to handle that exception in any case and need to re-try the insertion with a newly created ID. Adding this whilst keeping the pessimistic checking loop (that you would need to re-enter) will result in quite ugly and hard to follow code. Fortunately the solution to this is the same like the one to the drawback: Just go for it in the first place and try to store the data. In case of a UNIQUE KEY error just retry with a new ID.
Take a lookt at this article
Create short IDs with PHP - Like Youtube or TinyURL
It explains how to generate short unique ids from your bdd ids, like youtube does.
Actually, the function in the article is very related to php function base_convert which converts a number from a base to another (but is only up to base 36).
10 chars:
substr(uniqid(),-10);
5 binary chars:
hex2bin( substr(uniqid(),-10) );
8 base64 chars:
base64_encode( hex2bin( substr(uniqid(),-10) ) );
function rand_str($len = 12, $type = '111', $add = null) {
$rand = ($type[0] == '1' ? 'abcdefghijklmnpqrstuvwxyz' : '') .
($type[1] == '1' ? 'ABCDEFGHIJKLMNPQRSTUVWXYZ' : '') .
($type[2] == '1' ? '123456789' : '') .
(strlen($add) > 0 ? $add : '');
if(empty($rand)) $rand = sha1( uniqid(mt_rand(), true) . uniqid( uniqid(mt_rand(), true), true) );
return substr(str_shuffle( str_repeat($rand, 2) ), 0, $len);
}
If you do like a longer version of unique Id use this:
$uniqueid = sha1(md5(time()));
Best Answer Yet: Smallest Unique "Hash Like" String Given Unique Database ID - PHP Solution, No Third Party Libraries Required.
Here's the code:
<?php
/*
THE FOLLOWING CODE WILL PRINT:
A database_id value of 200 maps to 5K
A database_id value of 1 maps to 1
A database_id value of 1987645 maps to 16LOD
*/
$database_id = 200;
$base36value = dec2string($database_id, 36);
echo "A database_id value of 200 maps to $base36value\n";
$database_id = 1;
$base36value = dec2string($database_id, 36);
echo "A database_id value of 1 maps to $base36value\n";
$database_id = 1987645;
$base36value = dec2string($database_id, 36);
echo "A database_id value of 1987645 maps to $base36value\n";
// HERE'S THE FUNCTION THAT DOES THE HEAVY LIFTING...
function dec2string ($decimal, $base)
// convert a decimal number into a string using $base
{
//DebugBreak();
global $error;
$string = null;
$base = (int)$base;
if ($base < 2 | $base > 36 | $base == 10) {
echo 'BASE must be in the range 2-9 or 11-36';
exit;
} // if
// maximum character string is 36 characters
$charset = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
// strip off excess characters (anything beyond $base)
$charset = substr($charset, 0, $base);
if (!ereg('(^[0-9]{1,50}$)', trim($decimal))) {
$error['dec_input'] = 'Value must be a positive integer with < 50 digits';
return false;
} // if
do {
// get remainder after dividing by BASE
$remainder = bcmod($decimal, $base);
$char = substr($charset, $remainder, 1); // get CHAR from array
$string = "$char$string"; // prepend to output
//$decimal = ($decimal - $remainder) / $base;
$decimal = bcdiv(bcsub($decimal, $remainder), $base);
} while ($decimal > 0);
return $string;
}
?>