Image processing

[SPIP 1.8] allows you to use the image processing systems installed in your server. These SPIP functions were introduced in version 1.7 are both enhanced and more powerful.

SPIP uses three different methods for image processing:

— creating thumbnails of images installed as "joint documents". This was already available in version 1.7; [SPIP 1.8] allows you to apply to each image in these “portfolios”, a 90° rotation. This is particularly interesting when you install a series of photographs from a digital camera.

— in many locations in the private area the display of "vignettes".... that illustrate the navigation..... sections and even authors. For example, if we issue ..... to participants of a site for authors’ logos, vugnettes of these logos will appear alongside these authors’ messages in the forums in the private space;

— in the templates, webmasters have at their disposal the function reduire_imagewhich is particularly helpful for managing the layout and for creating different versions (in different sizes) of the same image. We can only encourage webmasters to "play around" with this function in order to enrich and control their graphical interface. You may as a result benefit from the following advantages:

• perfect alignment of images (for example, all images of the same width) without having to install images of a predefined size;
• a garantee that the layout will not degrade if an editor installs an oversized image;
• simple hovering and animation effects created with the same images in different sizes (without having to play around with "hovering logos")
• snappy portfolio (photo galleries) interfaces...

However, to process images SPIP has relies on systems that can not be automatically installed with SPIP but should instead be present on the server hosting your site. Consequently these systems have to be available alongside SPIP. In other words, SPIP alone is not sufficient for image processing. These functions should also be available.

You can chose the image processing systemin the "Advanced functions" page of the "Site configuration" in the private area. SPIP allows you to chose from 5 different methods.

Imagemagick

Imagemagick as a PHP extension is SPIP’s first choice. SPIP can detect its presence. This means that if Imagemagick is available on your server, SPIP will automatically use it.

SPIP will only allow you to choose from other methods if Imagemagisk is not available on your server. These methods are only just, if not at all detectable by SPIP, thus a vignette is displayed for each method, or else none at all if the method does not work on your site. You may then select your preferred method (sometimes, you can’t but select the only one possible!).

GD, GD2

GD (and its more powerful version 2) is a PHP extension now widely available on servers including shared hosting servers.

If GD2 is available it is worth using it as it produces good quality results.

On the other hand, GD (as in: "version 1 of GD") is suggested as a last resort. Indeed GD processes images using 256 colours thus introducing great loss in information in images. Therefore, you should only use it if no other method is available on your site.

Imagemagick by convert

Convert is the command line manager of Imagemagick. The quality is astounding although its installation is somewhat complex.

Once convert is installed on your site, you should configure the path in mes_options.php3 (it is a command line call) with the following variable:

At this point, you should enter the full path to the programme. Under Linux, this path is usually:

Under MacOS X, if installed with Fink:

These values are only indicative. Like all other programmes, it can be installed anywhere...

NetPBM

This method consists of three already old programmes that allow you to carry out the resizing of the image. The advantage of such a method is that these programmes can be installed without root access on most of the hosts.

You can find a clear explanation and pre-compiled versions of NetPBM on the site of the gallery application.

When using SPIP you should configure the path to pnmscale (only one of the three installed programmes, the other two should follow as the programmes are all installed in the same directory) with the following variable:

Once more it is up to you to determine the actual path of your installation.

* *

As a reminder you may obtain significant useful information on your system via the page /ecrire/info.php3, especially:
— the system you are using (this is useful in order to install the precompiled NetPBM);
— the PHP version;
— the potential availability of GD, GD2 and Imagemagick extensions.

Finally, should you encounter a problem, the best solution would be to contact your host so that he can install the necessary extensions if none is available. The availability of at least one PHP graphic extension on your host’s server is now the norm. Thus do not hesitate to ask for their installation which you will benefit from on your site.