(v13) OPI image replacement

This page applies to Harlequin v13.1r0 and later; and to Harlequin Core but not Harlequin MultiRIP.

The Open Prepress Interface (OPI) specifies a set of PostScript language comments that identify images in a PostScript language job and the characteristics and location of files containing alternative images; these are usually at a higher resolution, which can be substituted.

Using OPI leads to an improvement in network and computer performance, when dealing with large images, and is a widely accepted method of implementation. In addition, OPI provides support for parallel-processing workflows, where one user can be designing a page and another manipulating the images to be used when printing that page.

The following steps describe the basic OPI process.

The steps can be changed or even omitted. For example, a low-resolution FPO (For Position Only) image can be (manually) created before the final high resolution image is available.

1.  High-resolution images are placed on a server.
2.  From the high-resolution images, low-resolution, FPO images are generated and made available to desktop applications. These low resolution versions are called “Proxy images”.
3. The desktop application uses the low-resolution images as placeholders.
4. The PostScript language files generated by desktop applications are written with OPI comments and are significantly smaller and can be transferred across the network and processed much faster than they would normally.
5. The high-resolution image may undergo some changes such as retouching or color correction.
6. At print time, the FPO image is replaced by the original high-resolution image thus maintaining quality.