[atutor.git] / mods / photo_album / classes / phpThumb_1.7.2 / docs / phpthumb.faq.txt

//////////////////////////////////////////////////////////////
///  phpThumb() by James Heinrich <info@silisoftware.com>   //
//        available at http://phpthumb.sourceforge.net     ///
//////////////////////////////////////////////////////////////
///                                                         //
//    Frequently Asked Questions (FAQ) about phpThumb()     //
//                                                         ///
//////////////////////////////////////////////////////////////


Q: My question isn't answered here and I can't find any
   forums, how do I get support?
A: Please email me directly at info@silisoftware.com with
   any questions, suggestions, donations, etc.


Q: I think I found a bug, what's the first thing I should do?
A: Please make sure you're using the latest version. There's
   a good chance I may have already fixed the bug, so please
   make sure you can reproduce it with the latest version
   before reporting the bug.


Q: phpThumb doesn't work as expected, and it may be a server
   configuration issue -- how do I check?
A: Please run /demo/demo.check.php to find out how your server
   matches up with the recommended configuration and for
   suggestions on what to change for improved performance.


Q: What is the GPL? Can I use this for commercial sites?
A: See the GPL FAQ: http://www.gnu.org/licenses/gpl-faq.html
   In general, if you just want to call phpThumb.php in the
   standard <img src="phpThumb.php?src=pic.jpg&w=100"> manner
   then there is no problem, you're free to do this no matter
   if you site is commercial or not, or what license your code
   is released under.
   If you're calling phpThumb() as an object then you will
   probably run into license issues, so consult the above FAQ
   and the GPL itself.
   No matter if you use phpThumb() commercially or not, no
   payment is required. However, donations are always welcome
   and can be made at http://phpthumb.sourceforge.net


Q: Some images generate thumbnails, but some fail (the original
   non-resized image is output instead).
A: Your PHP installation does not have a high enough memory_limit
   and ImageMagick is not installed on the server. The PHP memory
   required is 5 times the number of pixels in the image.
   For example:\r
     640x480x5   = 1.5MB\r
     1600x1200x5 = 9.2MB\r
   You can adjust the PHP memory limit in php.ini (if you have
   permission on your server to do so), or (better yet) install
   ImageMagick on the server and that will bypass the memory limit
   issue. If you can't do either of the above, you can resize the
   images manually (with your favourite image editor) to a size
   that your memory_limit setting can handle, and/or you can
   re-save the images with an image editor that can embed an EXIF
   thumbnail (Photoshop for example) which phpThumb can use as an
   image source (lower image quality, but perhaps better than
   nothing).\r


Q: I'm getting is this error message:\r
   Failed: RenderToFile(<filename>) failed because\r
   !is_resource($this->gdimg_output)\r
A: You missed the call to GenerateThumbnail() before
   RenderToFile() or OutputThumbnail.
   See /demo/phpThumb.demo.object.php for an example.


Q: I'm trying to save a phpThumb-generated image in Internet
   Explorer and it saves in BMP format, why?
A: This is not phpThumb's fault, it is an IE issue:
   http://support.microsoft.com/default.aspx?scid=kb;en-us;810978\r
   http://support.microsoft.com/default.aspx?scid=kb;en-us;260650\r


Q: PNG images with transparent areas show up with gray background
   in the areas that are supposed to be transparent.
A: Internet Explorer has had a broken PNG alpha-channel display
   implementation for a decade, so it may never get fixed. Other
   major browsers generally handle alpha-transparent PNGs fine.
   See http://www.silisoftware.com/png_transparency/
   For an alpha-channel PNG display in IE hack, see this page:
   http://www.koivi.com/ie-png-transparency/


Q: I'm getting "<filename> does not exist" when I know the
   file does exist
A: Check that these two values are present and properly
   configured in phpThumb.config.php (introduced in v1.6.0):
    $PHPTHUMB_CONFIG['allow_src_above_docroot']  (default=false)
    $PHPTHUMB_CONFIG['allow_src_above_phpthumb'] (default=true)
   If your images are outside DOCUMENT_ROOT then you will have
    to configure 'allow_src_above_docroot' to true.
   Make sure whatever user the webserver is running as has read
    permission to the file/directory you're reading from\r


Q: Should I use phpThumb.php, or use phpThumb() as an object?
A: phpThumb.php is easier to use (less coding) for basic uses.
   phpThumb.php handles all caching; your own object will need
   to have its own caching code. If you just want to display a
   thumbnailed version of an existing image, use phpThumb.php
   If you want to render one (or more) thumbnails to static
   files (during upload, for example), that's an appropriate
   use for the object mode. Also, phpThumb.config.php is only
   used by phpThumb.php, so if you instantiate your own object
   you need to manually set all configuration options because
   phpThumb.config.php has NO effect. So, to repeat:
   **always use phpThumb.php unless you NEED to have an object**


Q: The first time I go to a page which contains thumbnails I
   don't actually see the thumbnail, I just get a browser image
   placeholder (or no image). As soon as I hit refresh, all the
   thumbnail images pop into place really fast.
A: You can try and see if it works better with\r
     $PHPTHUMB_CONFIG['cache_force_passthru'] = false;\r
   but typically the default setting works better.
   This is something of an unresolved issue on some servers,
   where for whatever reason I haven't (yet?) been able to
   figure out a setting that always works the first time. If the
   above config setting doesn't help, you might be stuck with
   having to manually or automagically pre-cache thumbnails as
   they're created.  Please email info@silisoftware.com if you
   have a better solution...


Q: Are there any front-end GUI interfaces to phpThumb()?
A: See /demo/readme.demo.txt


Q: Are there / have there been any security issues in phpThumb?
A: http://secunia.com/product/5199/


Q: Why can't Flash work with images output from phpThumb()?
A: Flash doesn't like progressive JPEG. Set:
   $PHPTHUMB_CONFIG['output_interlace'] = false;


Q: Image quality is not very good - why?
A: If you're using GD v1.x, no way around it. Upgrade to GD v2.x


Q: Image quality is very bad, very pixelated -- why?
A: You may be trying to resize images larger than the available
   PHP memory, so phpThumb is simply extracting and using the
   EXIF thumbnail as the image source, which is usually about
   160x120 (so if you resize it to 640x480 it will look very bad).
   To calculate the required size for memory_limit in php.ini,
   calculate the number of pixels in the image and multiply by 5:
   For example, 1600x1200 = 1600 * 1200 * 5 = 9600000 = 10M
   Easy solution: install ImageMagick


Q: Can I save the generated thumbnail to a file?
A: Yes, there are several ways to do so; the best way is to call
   phpThumb as an object and call RenderToFile() to save the
   thumbnail to whatever filename you want.
   See /demo/phpThumb.demo.object.php for an example.
   The other way is to use the 'file' parameter (see
   /docs/phpthumb.readme.txt) but this parameter is deprecated
   and may not exist in future versions of phpThumb().\r


Q: "Off-server thumbnailing is not allowed" -- how do I enable it?
A: By default, phpThumb() only makes thumbnails for the same
   domain that it is running on. To allow it to make thumbnails
   for a limited number of other domains, add them
   (in phpThumb.config.php) like this:
     $PHPTHUMB_CONFIG['nohotlink_valid_domains'] = array(
        @$_SERVER['HTTP_HOST'], 'example.com', 'www.example.com',
        'subdomain.example.net', 'example.org');
   To disable off-server thumbnail blocking, just set:
     $PHPTHUMB_CONFIG['nohotlink_enabled'] = false;


Q: Is it possible to set the parameters (like w/h/fltr[]) in
   the config, so that they can't be changed over the URL?\r
A: Take a look at $PHPTHUMB_DEFAULTS at the bottom of
   phpThumb.config.php  You'll want to set
     $PHPTHUMB_DEFAULTS_GETSTRINGOVERRIDE = false\r
   possibly also
     $PHPTHUMB_DEFAULTS_DISABLEGETPARAMS = true\r
   You may also want to investigate
     $PHPTHUMB_CONFIG['high_security_enabled'] = true
   (see the example at the bottom of phpThumb.config.php
   for how to call images in HighSecurity mode)


Q: Is there a way to use phpThumb() object to create thumbnails
   without the parameters in the URL showing the location of
   the image etc?\r
A: There is a demo in /demo/phpThumb.demo.object.php. You could
   modify this into your own file, but there still remains the
   problem of passing parameters to the file, whether it's
   phpThumb.php or your own instantiation of a phpThumb() object.
   I would suggest is putting as many of the common parameters
   into phpThumb.config.php as possible under $PHPTHUMB_DEFAULTS,
   so you then don't have to pass them for each image. If you
   don't want people modifying the parameters, turn on
   $PHPTHUMB_CONFIG['high_security_enabled'] and set a password
   (you'll need to generate the <img> tags with phpThumbURL()
   provided at the bottom of phpThumb.config.php). If you don't
   want people accessing your source images at all, you can
   place them outside DOCUMENT_ROOT on your server (as long as
   phpThumb/PHP has read access to the directory). The other
   option is to put your source images in a MySQL database
   and set $PHPTHUMB_CONFIG['mysql_query'] and related
   parameters in phpThumb.config.php to pull your source images
   from the database. That way it's impossible to retrieve the
   images except through phpThumb.php, and if high_security is
   enabled, then nobody can modify the parameters to view
   anything except what you want to show. So, yes, it's possible
   to use your own object, but it's probably better to use
   phpThumb.php if possible -- one notable issue is that
   phpThumb.php handles all the caching, so you're on your own
   to deal with that if you create your own object.


Q: How do I write the output thumbnail back to a database instead
   of outputting to the browser or a file?
A: See /demo/phpThumb.demo.object.php  Basically you need to call
   $this->GenerateThumbnail() then $this->RenderOutput() and then
   the output raw image data is found in $this->outputImageData


Q: phpThumb runs slowly, as if the images aren't cached, when I use HTTP source
   images (not on my server). How can I make it go faster?
A: $PHPTHUMB_CONFIG['cache_source_filemtime_ignore_remote'] = true;
   // if true, remote source images will not be checked for modification date and
   // cached image will be used if available, even if source image is changed or removed\r


Q: What does the "cache_default_only_suffix" configuration option do?
A: Cache files are normally created with big ugly names like
   "phpThumb_cache_www.example.com_src1a482c2c760463795ff18faf073b389f_par3e099041c2f4a73041a7f5d7e7fc481a_dat1119952152.jpeg"
   but if cache_default_only_suffix is enabled, cache filenames are simplified to
   "pic_thumb.jpg" (for example). The problem is that only one version of that
   thumbnail is possible, and you can never call it again with a different size,
   or different filters, etc.  Generally you don't want that enabled, but it's
   there because some people asked for it.


Q: Why is the visual size of rotated images smaller than the unrotated images?
A: phpThumb fits the rotated image into the 'w' and 'h' dimensions.
   Try not specifying a 'w' parameter: phpThumb.php?src=file.png&ra=15\r
   That should leave the image the apparent same size as the unrotated image
   (in actual fact the canvas size is enlarged to fit the rotated image in it).\r


Q: How can I purge cached files when I delete the source image?
A: You can either let phpThumb's built-in cache purging features (see phpThumb.config.php)
   take effect, or you can manually walk through your source images to delete and find
   the matching cache files and delete them:
     if ($dh = opendir($sourcedir)) {
       while ($file = readddir($dh)) {
         if ($file == $WhatIwantToDelete) {
           $md5 = md5_file($sourcedir.'/'.$file);
           unlink($phpthumb_cache_dir.'/phpThumb_cache_www.example.com_src'.$md5.'*.*');
         }
       }
       closedir($dh);
     }


Q: What is the proper name for this script/program/library?
A: The official name is "phpThumb()" but it may be written
   as simply "phpThumb" in short form (or where parentheses
   are not permitted), or "phpthumb" in case-insensitive
   environments. The following is a non-exhaustive sample of
   unacceptable forms: PHPthumb; phpThumbs; phpthump;
   phpthumbnailer; phpThumbnail; PHP Thumb; Phpthumb; etc.