ImageGlue is PostScript compatible which means that it can be used to render PostScript and related file formats such as EPSF (Encapsulated PostScript) and PDF (Portable Document Format).

PostScript related formats are unusual in that they contain a set of drawing instructions rather than an array of colored pixels. These drawing instructions are often highly specific describing actual amounts of ink to be placed by a particular type of printer onto a particular type of paper. These factors mean that rendering this type of format for display on a computer monitor may require that you use Image Manipulation parameters like Res and ColorSpace.

ImageGlue handles raw PostScript which conforms to the PostScript Language Document Structuring Conventions Specification (see Adobe Technical Note #5001 for details). This is necessary because PostScript which does not conform to this standard lacks important information such as image size and PostScript version identifiers.


Server Load    

PostScript rendering is a computationally expensive task. A typical EPSF or PDF will take some seconds to render and it is not uncommon to find complex images that will take some minutes to process. You can specify a Timeout when you render a PostScript related file and if the amount of time taken exceeds the timeout then ImageGlue will abandon the process.


Server Security    

PostScript is a programming language with a sophisticated set of commands. As such a PostScript file is a program which must be run in order to produce a rendered output. In its rawest form a PostScript program may have full access to the local file system and it is entirely possible to write malicious PostScript applications.

To prevent damage caused by malicious PostScript programs there are a number of levels of security in place. Your first level of security is the fact that PostScript program is run inside a sandbox which allows read-only access to the file system. The second level of security is determined by the security settings you configure for IIS. This means that you should ensure that your IIS security settings are sufficient to prevent unauthorized access to any sensitive resources.

To process EPSF or PDF files an intermediate file may be written to the 'WINNT/Temp' or 'WINNT/Temp/ImageGlue' directories. Both the IUSR and the IWAM must have full access to these files. If security denies access the render will fail.


GNU Ghostscript    

By default ImagGlue uses its own Advanced PostScript engine for rendering PostScript files.

However it is possible to configure ImageGlue to use GNU Ghostscript for rendering PostScript files.

To do this you will need to install Ghostscript (available from the WebSupergoo download page). You will then need to disable the ImageGlue PostScript engine either from code (via the modules parameter) or via the Modules tab of IGSettings.

GNU Ghostscript is a set of Open Source software that provides an interpreter for the PostScript language and for PDF. When ImageGlue is asked to render a PostScript related image it delegates this rendering task to Ghostscript and returns once the image has been completed.

ImageGlue may be aggregated with GNU Ghostscript. This means that ImageGlue and GNU Ghostscript are separate pieces of software and can be used completely independently of each other. The license agreements that apply to ImageGlue do not apply to GNU Ghostscript and the license agreements that apply to GNU Ghostscript do not apply to ImageGlue. You can replace an installed version of Ghostscript with a different version if you require and if you do not require GNU Ghostscript you can remove the entire application.