EtherShare "Open Prepress Interface" (OPI) is a server software that facilitates the handling of huge image files and has been adapted to the workflow in a typical prepress environment.
At first, you scan your original image with an adequate (comparatively high) resolution. Then, you retouch this high-resolution image using an image processing application (such as Photoshop) and save the result. As soon as the new high-resolution original image file is saved on an EtherShare OPI server, the OPI software automatically generates a low-resolution duplicate (a so-called layout) that needs much less memory. OPI-compatible layout applications - such as QuarkXPress, PageMaker, or FreeHand - on the network clients can work with these small low-resolution substitutes which leads to a reduction of processing time. All modifications like positioning, scaling, or rotating are marked by OPI comments which are inserted in the PostScript text file when you launch the print command. During printing, the modifications are applied to the high-resolution original images that now replace the low-resolution substitutes.
With this concept, huge image files are completely kept away from the client computers in a network. Thus, printing from a client is much faster and the network traffic is reduced.
Fig.
1 shows a prepress environment and illustrates how you can benefit from an EtherShare OPI server.
Fig. 1: The handling of image files on an EtherShare OPI
server
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The OPI standard and the syntax and structure of OPI comments were created by Aldus Corporation that now belongs to Adobe Systems, Inc.
3.2 Special features of EtherShare OPI 2.1
EtherShare OPI 2.1 is compatible to the Adobe OPI 1.3 and 2.0 specifications. In the following, we briefly explain the concepts of the HELIOS OPI product and describe the most significant features of the new program version 2.1.
EtherShare OPI 2.1 automatically generates layout files as soon as an image file is created or changed. Alternatively, however, you can generate layout files manually, using EtherShare OPI UNIX commands.
You are not restricted to a given image repository. You can keep your original high-resolution images on different volumes and in different folders. The low-resolution layout substitutes are automatically added to the folders that contain the originals. If you move any high-resolution images to another location, the OPI server will automatically look for these images whenever he needs them for printing.
You can define a default resolution value for all layout images, but it is also possible to specify an individual value for every folder. This is done by simply integrating the desired value into the folder name.
For the EtherShare OPI administration, you only need very few menu-driven dialogs that have been integrated into the EtherShare Admin program which is also used for the configuration of the EtherShare network.
A variety of
file formats
The new EtherShare OPI supports much more image file formats than the older version, e.g. Photoshop Native. For more details, please check the lists given in chapter
5 "Before getting started...".
Built-in color management
Our software package contains ICC profiles for a lot of different devices. You can use these profiles for color matching. EtherShare OPI 2.1 recognizes embedded ICC profiles in high-resolution images and supports tagging-by-reference where only a reference to the profile is embedded in the image file.
EtherShare OPI 2.1 offers provisions for proof printing. You can define profiles for both, your final output device (printer or press) and a proof printer (e.g. a color LaserWriter). Thus, if you print to the proof printer, you will obtain a very close simulation of the colors your final output device would produce.
Provisions
for printing layouts
"OpenImage"
extension
architecture
HELIOS provides for the OPI software an extension architecture called "OpenImage". With this architecture, third party software developers can easily add plug-ins or extensions to EtherShare OPI 2.1. For the "HELIOS OpenImage Software Developer Kit" developers should contact the HELIOS Software GmbH.
Compression of OPI images in PostScript Output
EtherShare OPI 2.1 supports new major compression features which can be turned on for each OPI queue. This considerably reduces the size of the PostScript printing data. Depending on the PostScript version used on the printer, different settings allow for reducing the amount of output data. The complete output compression is done "on-the-fly" during printing. This means there is no overhead that data first need to be written to disk before being processed by other programs.
The OPI output compress feature can considerably reduce the amount of data. The CCITT Group 4 compress is the best lossless linework compression available and can easily reduce linework files up to 50 times. It can be used with PostScript Level 2 or higher printers. The ZIP compression, which is available with PostScript 3 compatible printers, is the best lossless continuestone compression. The "Compress"-compatible compression works with PostScript 2 and 3 and has good compression results. The JPEG- compatible compression will lose always some image details but offers the best data reduction, it is supported with PostScript Level 2 or higher. Read
Bitmap: and
Monochrome: Color: in chapter
6.5 "Printer queue settings".
Please note that a fast printer with a fast network connection may process uncompressed data faster than compressed data. EtherShare OPI's additional compression also needs additional CPU time to reduce the data; individual testing will show which settings are perfect for the customer output options.
Colorized background images in XPress
EtherShare OPI 2.1 supports background colorization of Black & White and Grayscale TIFF images. Foreground colorized images have already been supported in the previous version. EtherShare OPI 2.1 supports both types foreground and background colorized images.
To enable these features EtherShare OPI 2.1 includes the extension "HELIOS OPI TuneUp XT" for QuarkXPress 3 and 4 which can be used with any XPress version including Asian versions. The extension includes additional OPI comments in the print job which allow to colorize images during the OPI replacement.
Colorized Pictures in PDF
EtherShare OPI 2.1 supports colorized foreground and background Black & White and grayscale layout images in PDF files which have been created with XPress and the Distiller. Printing to a spooler with Acrobat or PDF Handshake, EtherShare OPI will replace and colorize images during the output.
Temporary layout images under Mac OS 9
An outstanding problem was that former EtherShare OPI versions create unnecessary temporary layout files of Photoshop-saved images. The problem occurs with Mac OS 9 only and is now solved in EtherShare OPI 2.1.
The new EtherShare OPI 2.1 is able to work on Unicode volumes which can be shared between Macintosh and Windows stations. Old style EtherShare as well as new UTF8 volume charsets are fully supported. PCShare 3.0 support includes UTF8 volume charsets, long file names, and file locking. The PCShare support is only enabled if PCShare is licensed either by a demo or full license. OPI does not take any precautions of keeping file names in the 8.3 syntax when creating layout files, etc. These files will then not be seen anymore by old PCShare 2.5 clients.
The "opitouch" command can be used to create OPI layout files from high-resolution images which can be done as well with the "layout" command. The benefit of the "opitouch" command is that it uses the same "opisrv" queue and global OPI parameters as well as the OPI folder options for layout generation. This is the same as saving images from a Macintosh or Windows client using EtherShare and PCShare.
