Introducing TBXOPI, a PTBX application

TBXOPI is a second-generation OPI implementation with the following goals:

• Ultra-reliable, "lean-and-mean" image inclusion
• Fully scalable and embeddable
• Fully nested file-within-file capability
• Versatile, modular preview file generation
• Operators do not need to select OPI functions within the layout program
• Integrated with all PTBX services
• Seamlessly merges with existing workflows
• Uncluttered with non-OPI functions

If you want to know more about what OPI means, read this explanation.

While it is much more effective to use TBXOPI's native format, TBXOPI does implement the traditional OPI specification v1.3.

Native TBXOPI uses self-contained Encapsulated Postscript (EPS) files. On input, high-resolution images of a variety of formats are converted to a standard PC-format EPS file, with a preview part, and a postscript part. The postscript part contains dimensional information and a special reference comment identifying the high-resolution file. These files are called "stub" or "reference" files.

Because the stub files contain a preview and dimensional information, they can be used directly in layout programs. Any special treatment like run-arounds, will be placed in the output file as normal layout program behaviour. On output, the reference comment is replaced by the high-resolution image, converted to PostScript if necessary.

Introduction to OPI

Nowadays, "an OPI" is commonly used to mean the software application which implements the "OPI" specification. "OPI" stands for "Open Prepress Interface" and was invented by Aldus Corporation to make the use of high resolution images much more efficient on slow networks. Aldus also invented TIFF, and the original OPI was intended to allow TIFF images to be replaced in a PostScript output file.

Layout artists had to know about this "Traditional OPI" in order to be able to use it.

The principle of OPI is simple. Beacuse only low-resolution files are used in making up a layout, the amount of network traffic (or event disk traffic on a local disk) is reduced whenever the layout program uses the image data.

• When high-resolution images are saved on a computer, low-resolution copies are made and saved in a separate place.
• Layout users work with the low-resolution versions.
• On output, the low-resolution images are replaced by the high-resolution versions. The instructions for this were held in special PostScript comments which must appear in the output file.

OPI implementations largely automate this process.

Users of the traditional OPI had to tell the layout program that they were using it, so that the correct instructions could be placed in the output file. Otherwise, the program would assume that the inserted images were for output directly.