Gerald Richter > Apache-ImageMagick-2.0b7 > Apache::ImageMagick

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NAME ^

Apache::ImageMagick - Convert and manipulate images on the fly

SYNOPSIS ^

 In httpd.conf or .htaccess

 <Location /images>
 PerlFixupHandler Apache::ImageMagick
 PerlSetVar AIMCacheDir /var/aimcache
 </Location>   

 Then request

 http://localhost/images/whatever.gif/Annotate?font=Arial&x=5&gravity=west&text=Hello+world+!
 http://localhost/images/whatever.jpg

DESCRIPTION ^

This module uses the Image::Magick library to process an image on the fly. It is able to convert the source image to any type you request that is supported by Image::Magick (e.g. TIFF, PPM, PGM, PPB, GIF, JPEG and more). The requested fileformat is determinated by the fileextention of the request and Apache::ImageMagick will search for an image with the same basename and convert it automaticly (unless you set AIMDisableSearch). Addtionaly you can specify (multiple) image manipulation filters in the additional path info, and format options in the query string. All filters applied in the order they apear in the path info. A list of available filters can be found at http://www.imagemagick.org/www/perl.html#mani . As of this writing there are 67 very powerfull filters available. The parameters you give in the URL are passed to all filters. So the URL

 http://localhost/images/whatever.gif/Frame?color=gold

will request the image whatever.gif and apply the filter Frame and pass the parameter color with the argument gold to it, so you end up with a golden frame around that image. Addtionaly you can give all parameters that allowed in the Set method (see http://www.imagemagick.org/www/perl.html#seta ), for example to set the quality of your jpeg image you can use

 http://localhost/images/whatever.jpg?quality=10

A filter croaks on parameters it doesn't knows, so there is a problem when you give multiple filters different parameters. To distiguish the parameters for different filters or to give the same parameter with different values to two filters you can prefix the parameter name with the filter name separated by a colon:

 http://localhost/images/whatever.gif/Frame/Shade?Frame:color=gold&Shade:color=true

This will again draw a golden frame and will additonaly add a colored shadow. The parameters for the Set method a prefixed with Set:

 http://localhost/images/whatever.jpg/Frame/Shade?Frame:color=gold&Shade:color=true&Set:quality=10

The AIMParameter configuration diretive can be used to set defaults and/or force parameters values. So you can say

 PerlSetVar AIMParameter "font=/usr/images/fonts/arial.ttf !color=red" 

By prefixing the parameter with an !, the parameter values is foreced, so it can't be overridden by parameters passed to the hanlder via th URI.

Caching

Since conversion takes time Apache::ImageMagick caches the result unless you turn off caching with the AIMCache directive. If a cached image is found Apache::ImageMagick does nothing, but let Apache serve it just like a normal image. To make cacheing work you normaly have to set the directory where to cache files. This is done with the AIMCacheDir directive. Of course the directoy must be writeable by your http daemon. If you set addtionaly the AIMCheckMTime Apache::ImageMagick always check if the source file is newer then the cached file.

Using Scripts to process images

Another powerfull features of Apache::ImageMagick are scripts. These scripts are called after the image is loaded and before any processing takes places. Such a script can modify all parameters or make operations on the image. There are two possible sorts of scripts. A per image script, the name is build by appending the extension given by AIMScriptExt to the filename and searched in the directory given by AIMScriptDir. So if AIMScriptDir is set to /usr/images/scripts and a request for whatever.gif comes in, Apache::ImageMagick looks for a script named /usr/images/scripts/whatever.gif.pl. If the script is found it is loaded into memory, compiled and executed. If the script is already in memory, Apache::ImageMagick checks if the scripts is modified and if not it is only executed, so the Perl code has to be compiled only when the script changes. If AIMScriptDir is not set, Apache::ImageMagick doesn't search for a per image script. There is a second sort of script the default one. The full path of this script is specfied by the AIMScriptDefault directive and is executed after the per image script was executed. So it is able to force some default values. Both sort of scripts takes four parameters. The Apache request record, the Image::Magick object of the loaded image, an arrayref which contains the names of all filters and a hashref that contains all arguments. You can use the Apache object to retrives any information about the request. You can make any operation on the image object and you can modify the filters and arguments parameters. Here is an example that forces any fontname to be searched in a certain directory with the extention ttf. This actualy causes Image::Magick to use true type fonts:

    use constant FONTPATH    => '/usr/images/fonts/' ; 
    use constant FONTDEFAULT => 'arial' ; 

    my ($r, $image, $filters, $args) = @_ ;

    my $font ;
    if ($args->{font})
        {
        $args->{font} =~ m#(^|.*/)([a-zA-z0-9_]+)# ;
        $font = $2 ;
        }
    else
        {
        $font = FONTDEFAULT ;
        }

    $args -> {font} = FONTPATH . $font . '.ttf' ;

    1 ;

Createing images from scratch

Instead of modifing an existing image you can also create one from the scratch. You do this by giving the -new=1 parameter. In this case Apache::ImageMagick will not try to read an exiting image form disk, but create an empty one. You can use a script to create whatever you like. Here is an example:

In your httpd.conf or .htaccess you should set at least the cache directory and the script directory:

    PerlSetVar AIMCacheDir /var/images/tmp
    PerlSetVar AIMScriptDir .

The '.' as script directory will cause Apache::ImageMagick to look in the directory where the requested image should be for a script. So if you request:

    http://localhost/images/button.gif?-new=1

Apache::ImageMagick will look in the images directory for script named button.gif.pl, which may look like the following. The script gets an empty image object along with the other parameters. The scripts creates the image and Apache::ImageMagick cares about saving the image:

    my ($r, $image, $filters, $args) = @_ ;

    $image->Set(size=>'30x105');
    $image->Read('gradient:#00f685-#0083f8');
    $image->Rotate(-90);
    $image->Raise('6x6');
    $image->Annotate(text=>'Push Me',font=>'/usr/fonts/arial.ttf',fill=>'black',
      gravity=>'Center',pointsize=>18);

    1 ;

Of course you can run normal filters on such a created image, so you might like to use a script like this, which creates an empty button, add the annotate filter and sets some defaults arguments for it:

    my ($r, $image, $filters, $args) = @_ ;

    $image->Set(size=>'30x105');
    $image->Read('gradient:#00f685-#0083f8');
    $image->Rotate(-90);
    $image->Raise('6x6');

    push @$filters, 'Annotate' ;

    $args -> {font}         = '/usr/fonts/arial.ttf' ;
    $args -> {gravity}      = 'Center' ;
    $args -> {pointsize}    = 18 ;


    1 ;

And request it with:

    http://localhost/images/button.gif?-new=1&text=Push+Me

Apache configuration directives

The following configuration directives are set via PerlSetVar and used to control the operation of Apache::ImageMagick.

AIMCacheDir

Directory for creating cached image files. Default: Directory of requested image.

AIMSourceDir

Directory in which Apache::ImageMagick looks for the source image files.

Default: Directory of requested image.

AIMStripPrefix

This is prefix is stripped from the filename, before it is append to AIMSourceDir. It's actually a Perl regex.

AIMScriptDir

Directory in which Apache::ImageMagick looks for a script that should be executed to modfiy the parameters before conversion. The name of the script is build by removing the AIMStripPrefix from the filename, append the result to AIMScriptDir and appending the extension given with AIMScriptExt. If no AIMStripPrefix is given the basename of the image is taken, the AIMScriptExt appended and searched in the AIMScriptDir. The special value '.' means the same directory as the source image itself. If AIMScriptDir is not set, no script is executed.

Default: No script is executed.

AIMScriptExt

Fileextention append to script name.

Default: pl

AIMScriptDefault

If given, this script is always executed before the image is created.

Default: No script is executed.

AIMCache

Turn caching off. Default: on.

AIMParameter

can be used to set defaults and/or force parameters values. It contains a space spearated list of parameter values pairs. If you need spaces inside your values, you have to quote the parameter/value pair.

Example:

 PerlSetVar AIMParameter "font=/usr/images/fonts/arial.ttf !color=red" 

By prefixing the parameter with an !, the parameter values is foreced, so it can't be overridden by parameters passed to the hanlder via th URI. If there is no ! then the parameter acts as a default value.

AIMDebug

Turn this on to get some debug info into the httpd error log. Default: off.

AIMCheckMTime

When set the modification time of the source image is compared to the time of the chached version. If the source is newer the it is recomputed. Default is off.

AIMDisableSearch

When set the search for a file with a different format is disabled. Default is the automatic search and conversion is on.

Non mod_perl frontend proxy ^

For performance reasons many people are running a setup with multiple Apache server, where you have a non mod_perl frontend that delivers static pages and images, while mod_perl requests are proxy to a mod_perl server. (like decribed for example here: http://perl.apache.org/guide/strategy.html#Apache_s_mod_proxy) If you are using Apache::ImageMagick every request to such an image must be handled by a mod_perl enabled server. When most requests are deliverd from the cache there is actualy no need to have mod_perl. For such situations Apache::ImageMagick comes with a Apache module, named mod_aimproxy, which will be linked in the frontend server. When a request comes in, the module first checks if the image is available from the cache. If yes the frontend server can deliver it directly, just like a static image. If no, the request is proxied to the backend mod_perl server. To get this working the uri of the request in the frontend and the backend must be exactly the same (expcet for the host and/or port part). Also you must configure the same cache directory. A setup for the frontend might look like

    AIMCacheDir /var/aimcache
    AIMProxyPassTo /images localhost:8765

and the corresponding backend setup

    <Location /images>
    PerlFixupHandler Apache::ImageMagick
    PerlSetVar AIMCacheDir /var/aimcache
    </Location>   

mod_aimproxy has two configuration directives:

AIMCacheDir

Give the location of the cache. Can only given once

AIMProxyPassTo

Gives the location for which mod_aimproxy should take care and a hostname and optional a portname, where the request should proxied to, if the image is not found in the cache.

This directive can be given multiple times, to cover different locations/backend hosts.

SUPPORT ^

As far as possible for me, support will be available via the modperl mailing list. See http://perl.apache.org.

AUTHOR ^

G.Richter (richter@dev.ecos.de)

Based on work from Lincoln Stein and Doug MacEachern publish in "Writing Apache Modules with Perl and C" see www.modperl.com

SEE ALSO ^

Perl(1)
Image::Magick
http://perl.apache.org
http://www.modperl.com
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