This is an example of using Gd / FreeType to generate image text labels with TTF font. Provided script could be used as "text rasterization service" to generate arbitrarily text-images for a web site. MD5-based authorization is used to avoid image generation by unauthorized users.
Compatible with:
PHP 5 or higher
PHP 4.1 or higher
Gd 2.x, FreeType support in PHP
Our "text rasterization service" does the following:
Receives text generation parameters(text and font-size) and md5 sign of secret key + parameters.
Checks(by md5 sign) if rasterized text image exists in cache directory. If so, sends it to web browser and quits.
Checks md5 authorization: computes md5 of secret key + parameters. If computed md5-sign equals to provided md5-sign, then request is valid. Otherwise — somebody else is trying to use our "text rasterization service".
Generates text image with imagettftext. Image size exactly matches text size (using imagettfbbox)
Sends generated image to browser
So, it is possible to automatically generate a lot of image text labels for a whole web site. Caching technique will decrease server load: images would be generated only once.
<?php
/*
Online PHP Examples with Source Code
website: http://4evertutorials.blogspot.com/
*/
// Checking for gd and Freetype support
if (!function_exists('gd_info'))
die('No gd support in PHP.');
$gd = gd_info();
if ($gd["FreeType Support"] == false)
die('No FreeType support in gd');
// If you're sure about gd & freetype support
// -- comment out this block
// directory for caching generated images
// should be writable
$cache_dir = '/home/path/to/cache'; // DO NOT FORGET TO CHANGE
// testing cache dir
// remove these lines if you're sure
// that your cache dir is really writable to PHP scripts
$tf = $cache_dir.'/'.md5(rand()).".test";
$f = @fopen($tf, "w");
if ($f == false)
die("Fatal error! {$cache_dir} is not writable. Set 'chmod 777 {$cache_dir}'
or something like this");
fclose($f);
unlink($tf);
// testing cache dir END
// full path to preferred TTF font
// you could change this to be HTTP parameter
$font = '/home/path/to/font/FuturaBook.ttf'; // DO NOT FORGET TO CHANGE
// md5 secret
$md5_secret_key = 'changeme'; // DO NOT FORGET TO CHANGE
// md5 sign of parameters
$auth_sign = isset($_GET['a'])?$_GET['a']:'';
// checking for cached file:
$cache_file = $cache_dir.'/'.$auth_sign.'.png';
if (file_exists($cache_file))
{
// if cached file exists
// output it and quit
header("Content-type: image/png");
readfile($cache_file);
exit();
}
// no cached file exists
// input parameters: text and size
$text = isset($_GET['text'])?$_GET['text']:'default';
$font_size = isset($_GET['size'])?intval($_GET['size']):30;
if ($font_size == 0) $font_size = 30;
//
// basic sign checking:
$computed_sign = md5($md5_secret_key.$text.$font_size);
// computing md5 sum of concatenation
// of secret key and parameters
// hmac-based alrorithm would fit this case more
// but for real-world purpose md5 of concatenation
// is enought
if ($computed_sign != $auth_sign)
die('Auth failed'); // auth error, provided sign is invalid
// getting bounding box
$bbox = imagettfbbox($font_size, 0, $font, $text);
// imagettfbbox returns very strange results
// so transforming them to plain width and height
$size_w = abs($bbox[2] - $bbox[0]);
// width: right corner X - left corner X
$size_h = abs($bbox[7] - $bbox[1]);
// height: top Y - bottom Y
// This is a lower-left corner
// but imagettfbbox() sets (0,0) point
// inside bounding box
// so we shifting lower-left corner
$x = -abs($bbox[0]);
$y = $size_h - abs($bbox[1]);
$im = imagecreatetruecolor($size_w, $size_h);
// creating image
$back = imagecolorallocate($im, 255, 255, 255); // background color
$fore = imagecolorallocate($im, 0, 0, 0); // foreground color
imagefilledrectangle($im, 0, 0, $size_w - 1, $size_h - 1, $back);
// filling with background color
imagettftext($im, $font_size, 0, $x, $y, $fore, $font, $text);
// rendering text
imagepng($im, $cache_file); // outputing PNG image to file cache
imagedestroy($im); // destroy image
// sending data from cache file
header("Content-type: image/png");
readfile($cache_file);
?>
To generate image 'Hello World', 90 pixels size you should call this script as (assuming you've saved it as font.php):
<img src="./font.php?text=Hello+World&size=90&a=4c9a240e98490275d845c96fdb8e5a19">
Note parameter 'a=4c9a240e98490275d845c96fdb8e5a19'. '4c9a240e98490275d845c96fdb8e5a19' is a result of md5('changemeHello World90'): concatenation of secret key, text and font size.
You could use some helper function to set script arguments, like 'image_params':
<?php
/*
Online PHP Examples with Source Code
website: http://4evertutorials.blogspot.com/
*/
$md5_secret_key = 'changeme';
// returns parameters and md5 sign for
// text generating service
function img_params($text, $size)
{
global $md5_secret_key;
$p = '?text='.urlencode($text).'&size='.$size.'&a=';
return $p.md5($md5_secret_key.$text.$size);
}
?>
<html><head><title>Test</title></head>
<body>
<center>
<img src="./font.php<?php echo img_params('Hello World', 90);?>">
</center>
</body>
</html>
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