Snippets Graphics
Graphics
imcache
by: Kern Herskind Hansen
|
August 11, 2003
Version: 1.0
Type: Function
Category: Graphics
License: GNU General Public License
Description: A simple function for caching images generated by php/gd. http://www.kern-online.dk/phps/imcache.phps
<?php
/**
* imcache (a function for caching images generated by php/gd)
*
* Copyright (C) 2003 Kern Herskind Hansen
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*
* Requirements:
*
* It requires GD library.
*
*
* Usage:
*
* To enable imcache in your image generating scripts, you have to do three
* things:
* 1) Include imcache.php (this file) in your script.
* 2) Wrap your image generating code in a function that returns an image handle.
* NOTE: Don't use imagepng()/imagejpg()/imagegif() in this function (this is
* handled by imcache function) and don't call imagedestroy($return_im_handle)
* on the image handle you are about to return!
* 3) Call imcache function with appropiate arguments:
* $cachepath - path to the directory where cached files should reside. Make
* sure that the webserver has write rights to the directory.
* $type - the type of image you want to output, must be either "gif", "jpeg"
* or "png".
* $function - string containing the function to call (see example)
*
*
* Example:
*
* <code>
* <?php
* function blankcanvas($xdim, $ydim)
* {
* return imagecreate($xdim, $ydim);
* }
* imagecache("./cachedimages", "png", "blankcanvas(10, $_GET['height'])");
* ?>
* </code>
*
* In the above example we have a function called blankcanvas that returns a
* handle to an image oh variable dimensions. Note how the last argument of
* imcache function looks; it's a string explaining how blankcanvas should
* be called...
*
*
* @author Kern Herskind Hansen <kern@kern-online.dk>
* @date 2003-09-04
* @license LGPL (http://www.gnu.org/licenses/lgpl.html)
* @changes 1.0 first version
*
*/
function imcache($cachepath, $type, $function)
{
// Compose a uniqe'ish filename for cacheing.
$filename = urlencode($_SERVER["REQUEST_URI"]) . "---" . urlencode($function);
$filepath = realpath($cachepath)."/".$filename;
if(file_exists($filepath) and filectime($_SERVER["PATH_TRANSLATED"]) < filectime($filepath))
{
// if a file is there - stream response directly
header("Content-type: ".image_type_to_mime_type(exif_imagetype($filepath)));
@readfile($filepath);
touch($filepath);
}
else
{
// if a file isn't there - call function that wil generate image
// first make sure that $function "looks" like a function call
if(ereg("^\s*[_a-z0-9-]+\s*\(.*\)\s*;?\s*$", $function))
{
$im = FALSE;
// adjust function exspression ... (it needs to start with "$im = " and end with ";")
if(!(ereg(";\s*$", $function)))
$function = $function.";";
$function = '$im = '.$function;
// black magic ;-)
eval($function);
header ("Content-type: image/$type");
switch($type)
{
case "gif":
imagegif($im);
imagegif($im, $filepath);
break;
case "jpeg":
imagejpeg($im);
imagejpeg($im, $filepath);
break;
case "png":
imagepng($im);
imagepng($im, $filepath);
break;
}
imagedestroy($im);
}
else
{
trigger_error('imcache: $function argument not valid, must be in the form "foo(arg, arg)" on line '. __LINE__ ." in ". __FILE__);
}
}
}
?>
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