ImageServer G8 User manual (Version 6.0.0)  

3 Before getting started

3.1 Backward compatibility

ImageServer supports backward compatibility to EPSF and TIFF layout files that have been generated by previous ImageServer versions.

EtherShare OPI 1.x will not be able to handle and understand layout files generated by ImageServer UB or newer. However, ImageServer 2.5 will handle them, provided it already supports the used image format.

Please note that if you are using EPSF layout files which were generated by EtherShare OPI version 2.1 or earlier, downsampling, color matching and other new features will not be supported when you print separations. In that case, you have to generate new layouts from the high-resolution original images and thus create layout files that can be subjected to all features available in the new program version. You may use the HELIOS “touch” program for regenerating layouts (detailed instructions are given in 5.5 “Refresh layouts using the “touch” program”), or the HELIOS “opitouch” command (see 6.2 “opitouch”).

3.2 About images, color modes, file formats, and compression

This section provides an overview of ImageServer supported file formats, color spaces, and compression options for layout file generation. It is equally applicable to image conversion using ImageServer Script Server.

3.2.1 General remarks

An image file is defined by its file format. In addition to that, it contains information about its color mode and the mode of compression. These three characteristics depend on one another and may not be combined arbitrarily. An example is given in the following illustration.

The characteristics that define a given image file

Fig. 3.1: The characteristics that define a given image file

Fig. 3.1, for example, shows a Photoshop CMYK image in the Scitex CT format, which cannot be compressed (unavailable options are grayed out in the illustration).


Please note that some file formats are already compressed (e.g. JPEG).

In the following, we will …

3.2.2 64-bit file offset support

ImageServer handles file sizes up to 64-bit, which equals 8.3 million TB (Terabyte). The old 32-bit support can only handle files up to 2 GB. This is important because image files today can easily exceed 2 GB.

3.2.3 Supported file formats

ImageServer provides OPI facilities and, in addition, contains built-in color management features. The software accepts different file formats for the generation of (low-resolution) layout files and it supports various file formats for color matching. Please note that some file formats in connection with specific color modes allow the generation of layout files, but do not allow color matching.

Table 3.1 lists all supported file formats for the generation of layout files (and their possible color modes), whereas Table 3.2 only lists those file format/color mode combinations that allow color matching. If you want to achieve predictable color results on your printouts, you should select for your image files one of the file formats listed in Table 3.2. Table 3.3 gives an overview of the image file formats that are supported by ImageServer.

File format Color mode
TIFF Bilevel, Grayscale, Indexed, RGB, CMYK, CIELab, Multichannel (e.g. Hexachrome), YCbCr*
EPSF raster- and object-based images Bilevel, Grayscale, Indexed, RGB, CMYK, CIELab, Spot, Multitones*
PICT Bilevel, Grayscale, Indexed, RGB
JPEG Grayscale, RGB, CMYK, CIELab, YCbCr*
JPEG 2000 Grayscale, RGB, CMYK, CIELab, YCbCr*
JBIG2* Bilevel
Scitex CT Grayscale, CMYK
Photoshop Bilevel, Grayscale, Indexed, RGB, CMYK, CIELab, Spot, Multichannel*
BMP Bilevel, Indexed, RGB
PNG Grayscale, Indexed, RGB
PDF** Bilevel, Grayscale, Indexed, RGB, CMYK, CIELab, Spot, Multichannel*
HELIOS raster PDF Bilevel, Grayscale, Indexed, RGB, CMYK, CIELab, Spot
DCS 1, DCS 2 CMYK, Spot, Multichannel*
Raw RGB*

Table 3.1: High-resolution file formats that are supported by ImageServer

* Currently read-only support
** PDF HandShake option
File format Color mode
TIFF RGB, CMYK, Grayscale, CIELab, Multichannel (e.g. Hexachrome), YCbCr*
EPSF raster-based images RGB, CMYK, Grayscale, CIELab
EPSF object-based images Not supported!
JPEG RGB, CMYK, Grayscale, CIELab, YCbCr*
JPEG 2000 RGB, CMYK, Grayscale, CIELab, YCbCr*
JBIG2* Bilevel
Scitex CT CMYK, Grayscale
Photoshop RGB, CMYK, Grayscale, CIELab, Multichannel*
BMP Bilevel, Indexed, RGB
PNG RGB, Grayscale
PDF** RGB, CMYK, Grayscale, CIELab, Multichannel*
HELIOS raster PDF RGB, CMYK, Grayscale, CIELab
DCS 1, DCS 2 CMYK, Multichannel*
Raw RGB*

Table 3.2: File format/color mode combinations that are supported for color matching

* Currently read-only support
** PDF HandShake option
File format Type Suffix
Tagged Image File Format TIFF .tif, .tiff
JPEG or JFIF JPEG .jpg, .jpeg
JPEG 2000 JP2 .jp2, .jpx
JBIG2 JB2 .jb2, .jbig2
Encapsulated PostScript File EPSF .eps, .epsf
DCS 1 EPSF/DCS 1 .eps, .epsf
DCS 2 EPSF/DCS 2 .eps, .epsf
Binary Encapsulated PostScript File EPSF/BIN .eps, .epsf
Binary DCS 1 EPSF/DCS 1 BIN .eps, .epsf
Binary DCS 2 EPSF/DCS 2 BIN .eps, .epsf
Scitex CT Handshake Format ..CT .sct
Adobe Photoshop Format 8BPS .psd, .psb
Macintosh Picture Format PICT .pic
Macintosh Picture format Version 1 PICT/1 .pic
Macintosh Picture format Version 2 PICT/2 .pic
Macintosh Custom Icon Family Format MacIcon
Adobe Path Resource Format AdobePath
BMP BMP .bmp
Portable Network Graphics File Format PNGf .png
HELIOS Document Preview (XPPV) XPPV .xpv
Portable Document Format (raster-based) PDF .pdf
Portable Document Format (object-based) PDF/Vector .pdf
Unknown UNKN

Table 3.3: File formats, image types and suffixes

3.2.4 File format characteristics

Before you save an image in an image processing application (or scan or digital camera system), you should make a decision on the file format you want to choose. The advantages and disadvantages of the different file formats are described below.


Again, the file formats have to be judged from different points of view. Some characteristics of a given file format may be advantageous in general, and for OPI processes, but – at the same time – disadvantageous with regard to color matching!

The format you choose for an original high-resolution image file determines the format of the generated layout file. Please refer to 3.2.6 “File formats of OPI-generated layout files” for explanations on the different layout file formats.

EPSF (raster-based)
EPSF (object-based)
JPEG 2000
Scitex CT
Photoshop native

3.2.5 Supported compression modes

ImageServer supports several file formats for the generation of layout files, even if the data contained in these files has been subjected to compression. The original high-resolution files remain compressed, but usually do not pass on the compression to the layout files. If you want the layout files to be compressed as well, you may use HELIOS Admin or the respective parameters (see 4.1 “ImageServer settings” and 6.1 “layout” for details). Table 3.4 lists various modes of compression supported by ImageServer and indicates whether they can be applied to the different file formats.

File format Compression mode
TIFF Compress°, CCITT RLE, CCITT G3 Fax, CCITT G4 Fax, JPEG, PackBits RLE, Flate (Zip)°
EPSF Compress***, CCITT RLE***, CCITT G3 Fax***, CCITT G4 Fax***, JPEG, Flate (Zip)
JPEG 2000 JPEG 2000°
Scitex CT Compress, CCITT RLE, CCITT G3 Fax, CCITT G4 Fax
Photoshop PackBits RLE
Photoshop PSB PackBits RLE°
ICS Compress***, CCITT RLE***, CCITT G3 Fax***, CCITT G4 Fax***
BMP PackBits RLE
PNG Flate (Zip)°
PDF** Compress, CCITT RLE, CCITT G3 Fax, CCITT G4 Fax, JPEG, JPEG 2000°, JBIG2, PackBits RLE, Flate (Zip)
HELIOS raster PDF Compress, CCITT RLE, CCITT G3 Fax, CCITT G4 Fax, JPEG, JPEG 2000, JBIG2, PackBits RLE, Flate (Zip)
DCS 1, DCS 2 Compress***, CCITT RLE***, CCITT G3 Fax***, CCITT G4 Fax***, JPEG

Table 3.4: Compression modes and their relation to different file formats

* Currently read-only support
** PDF HandShake option
*** This compression mode is allowed but will cause restrictions:
raster-based data is no longer recognized by ImageServer
° 16-bit compatible

3.2.6 File formats of OPI-generated layout files

The layout files that are generated by the OPI software are either EPSF or TIFF, by default, depending on the color mode and file format of the high-resolution original image.

EPSF layout files

The OPI server generates EPSF layout files if

TIFF layout files

TIFF layout files are generated of every high-resolution original image that


For additional information about PDF-native OPI workflow see “PDF-native OPI” in the HELIOS PDF HandShake manual.

EPSF and TIFF layout files

In the following, we briefly discuss the differences between EPSF and TIFF layout files. Knowing these differences can help you decide which layout file format you want to use. (You may then select the color mode and file format for your high-resolution original images and thereby indirectly determine the desired layout file format.)

There are mainly two aspects that make up the difference between EPSF and TIFF layout files:

Other layout file formats?

In most cases, it is convenient and sensible to accept the default EPSF or TIFF layout file format. Nevertheless, you may as well choose any other format for your layout files. 5.2 “Define folder specific OPI settings” explains how to set custom settings on a “per volume” or “per folder” basis.

Color modes for layout images

The color modes of the high-resolution originals are not passed on to the layouts. By default, layout images are Euroscale- or SWOP-CMYK, to allow the layout applications to print separations. In special situations, you may also select the RGB or Lab color mode for layout images (see Layout Color in 4.1 “ImageServer settings”).

3.3 About applications, OPI comments, and modifications

3.3.1 OPI-compatible applications

The ImageServer software requires two types of OPI-compatible applications, namely:

Image processing applications

Most scan systems and image processing applications are OPI-compatible as far as the “input” side is concerned. They all offer the possibility of creating at least one or two file formats that are supported by ImageServer for the generation of layout files and for color matching (e.g. TIFF-RGB or raster-based EPSF-CIELab). One of the most frequently used image processing applications is Adobe Photoshop – ImageServer supports the Photoshop Native format.

Layout applications

Strictly speaking, OPI-compatible layout applications have to meet two different demands: they have to be able to import/place layout images and they have to be able to generate OPI comments according to the Adobe OPI standard and place these comments into the PostScript that is generated for each print job.

There is, however, one exception from this rule: layout applications that are able to import EPSF layout files are quasi-OPI-compatible, even if they do not generate OPI comments. This is due to the characteristics of EPSF layout files which simply do not allow applications to modify their contents. If an EPSF layout file already contains OPI comments – e.g. a reference to the location of the original high-resolution image file – these comments are preserved and passed on to the PostScript file.


Some layout applications that are fully OPI-compatible also offer OPI options in their print dialogs, namely “Omit TIFF” and “Omit TIFF & EPS”, and thus provide additional means of speeding up print jobs when working with OPI. Details about the “Omit …” options are given in 5.6 “OPI print options – Printing from QuarkXPress and InDesign”.

The most frequently used layout applications that are – in principle – fully OPI-compatible are listed in Table 3.5.

Application Mac & Windows PC
QuarkXPress 3.1-9
InDesign 1.0 and higher

Table 3.5: OPI-compatible layout applications

Other applications like CorelDraw, FrameMaker, Word, and MS Publisher may also be involved in the process of creating documents that include text and images. Strictly speaking, they were not designed for layout purposes in prepress environments. These applications are – if at all – only quasiOPI-compatible, when they use EPSF layout files.

The mentioned restrictions are also applicable to layout applications for UNIX systems. Most of these applications are able to import EPSF layout files, and thus can be used with ImageServer.

3.3.2 Supported image modifications and OPI comments

Image modifications

Different layout applications provide different features for image modifications. Depending on your application, you can e.g. move, scale, rotate, skew, reflect, tint or crop your images, and apply a clipping path, or overprinting. All these modifications are supported by ImageServer and are automatically applied to the high-resolution original images during printing.


Transparency definitions for grayscale and color images are the only modifications that are not supported by ImageServer, due to limitations in the OPI specifications. You may overcome this limitation with the PDF-native OPI workflow, which is described in the HELIOS PDF HandShake manual.

OPI comments

If you print from a layout application, the OPI server requires different information about the images that are included in the document. There are several OPI PostScript comments that contribute to a complete image description. Some comments only serve to clearly identify the high-resolution image; others are used to describe the modifications that have been applied to the layout.

For example, the comments “%ALDImage Dimensions” and “%ALDImagePosition” define the dimensions and the position of an image, and thus may also include information about whether you have moved or scaled the layout image.

Image paths and clipping paths

In Photoshop, the outline of a selected area can be saved as a vector outline or path. Multiple paths can be created and saved with the file. One of the paths can also be selected as a clipping path. A clipping path can be activated to mask part of an image, so that only the desired portion is seen in the printout. Some page layout programs recognize and utilize these paths. However, the behavior varies depending upon the program and file format. For example, some applications have poor support for TIFF files containing paths, while others have excellent support. ImageServer can be set to produce layout files with the desired path properties for your specific page layout programs and objectives.

Multiple Photoshop paths

ImageServer supports multiple paths, any one of which may also be designated as the active clipping path. Multiple paths are migrated into converted files. Layout images inherit these paths if no path is defined as clipping path. If a clipping path is defined, only this is applied. Photoshop paths can be exported/imported into existing files, so users can re-use the images and use different paths for different jobs (see -o ImportMask <string:None> in 6.1.8 “Image conversion options” and 6.1.12 “Tagging options”). In layout applications such as QuarkXPress or InDesign, it is possible to select a defined path and make it the active clipping path.

TIFF files with clipping paths

Clipping paths can be saved within TIFF images in an image processing application. Even though the image will print correctly and the clipping path will be applied, some applications cannot display a TIFF clipping path, and hence are unable to properly use features such as text “Runaround”. Therefore, by default, ImageServer generates EPSF layout images of TIFF hi-res files that contain a clipping path. Layout applications can then properly display and use the clipping path.

If your layout application, e.g. QuarkXPress or InDesign, does support the TIFF clipping path feature then you can use either EPSF or TIFF layout images. Some applications also have the capability to add or modify the image clipping path in TIFF files. If you wish to take advantage of this feature, layout images should be generated in TIFF format (see 5.2 “Define folder specific OPI settings”). TIFF layout images will always inherit all paths from the high-resolution image.

PC-EPSF files with clipping paths

Unlike Mac-EPSF files, PC-EPSF files contain a TIFF screen preview of the respective image (instead of a PICT screen preview).


For the generation of PC-EPSF layouts see 4.2 “Volume settings”.

EPS files and clipping paths

Some layout applications lack full support for TIFF images containing a clipping path. For these applications, EPS layout images should be used (the server default). In this case, you need to specify whether the server image replacement should use the clipping path applied by the image processing application or the path applied by the page layout application. See 3.3.3 “Application clipping paths” for details.

3.3.3 Application clipping paths

A bitmap image file that already contains clipping path information and then has path changes applied in a layout program, may cause interferences and lead to unwanted results. HELIOS Admin offers an option (see checkbox Ignore Mask for Bitmap Images During Output in Fig. 3.2) that makes the server ignore existing masks for bitmap images so a new clipping path can be defined from within the layout application (QuarkXPress, InDesign, etc.). This option can also be set for individual folders via folder naming syntax (see 5.2 “Define folder specific OPI settings”).

HELIOS Admin <code>OPI Layout</code> preferences

Fig. 3.2: HELIOS Admin OPI Layout preferences


Multiple Photoshop paths are migrated into layout and converted files. Photoshop paths can be exported/ imported into existing files, so customers can re-use the images and use different clipping paths for different jobs.

Table 3.6 gives an overview on the compatibility of layout software programs and the used layout file formats which have application paths included.

Layout program Application path compatibility
InDesign CS1 or newer TIFF layout, JPEG layout, EPS layout, EPS layout with default application path
QuarkXPress 4-9 TIFF layout, JPEG layout, EPS layout

Table 3.6: Application path compatibility

Use always the folder specific option “%x” (see 5.2 “Define folder specific OPI settings”) or check the Ignore Mask for Bitmap Images During Output option.

3.3.4 Additional channels in bitmap images

ImageServer recognizes and supports additional channels (e.g. Hexachrome, spot colors or alpha channels). All additional channels will be used as spot color channels.

It is often required to ignore additional channels and use the default printing channels, e.g. CMYK, RGB or CIELab. Many layout applications ignore additional channels in order to be compatible with the printout. Printing from these applications, ImageServer can ignore additional channels (see Ignore Additional Channels for Bitmap Images in Fig. 3.2) server-wide or enable/disable this setting on a folder tree (see 5.2 “Define folder specific OPI settings”).

3.4 About output devices

PostScript Level 1&2, PostScript 3

ImageServer requires PostScript output devices for printing. There are three types of PostScript RIPs: Level 1, Level 2, and PostScript 3 compatible devices.

The Level 2 and PostScript 3 specifications are follow-ups to the Level 1 specification and provide many more features, as e.g. support for different color spaces such as CMYK, RGB and CIE-based color spaces, and provisions for color matching and transformations into CMYK.

PPD files

Different printers may behave differently and provide different features. PPD files contain comprehensive printer descriptions – with the supported PostScript level being only one aspect. ImageServer (just like any application) refers to the PPD file to get information about the features of the output device. So, for high-quality printouts, always make sure that you have activated a PPD file that properly corresponds to your current output device. For details, see the HELIOS Base manual.

Are PostScript levels relevant to ImageServer?

Usually, if you are printing with ImageServer, our software takes care about the separation into CMYK. The separation modules of the RIP are not required. Thus, print jobs do not depend on the final output device. It does not make any difference whether you are using a Level 1, Level 2 or PostScript 3 printer.

It is, however, possible to leave the separation to the PostScript RIP. In that case, you have to select the Lab D65 color space as output color space (see Default Printer Profile in 4.4 “ICC printer settings”) and you must use a Level 2 (or PostScript 3) output device. The RIP will then be initialized with a specific CRD (Color Rendering Dictionary) and, using this dictionary, will perform the separation into CMYK. This workflow may be sensible if you are sending your documents (e.g. a magazine) to different production sites. Your print job is not yet separated for a given output device and the Lab D65 color space is device independent. The different RIPs transform the color data into the gamut of the respective printer or press and the output results should all be identical. Please note that this workflow does not allow proof printing (see B “Colors, color matching, proof printing – basic concepts” for details about proofs).

3.5 How ImageServer modifies color modes

If you retouch an image using an image processing application, you also define a color mode for this specific image. This color mode will be preserved as far as the high-resolution original image file is concerned – but it will not be passed on to the layout file and may be changed for printing purposes, i.e. transformed into the color space of the output device.

In the following, we briefly describe how ImageServer handles or modifies color modes and thus relieves you of taking care about it.

Color modes for printing

The color mode OPI selects for printing depends on whether you print composite or separations and whether or not you have activated color matching. The color mode of the high-resolution original image does not matter, unless it is Bilevel or Grayscale – these two color modes are preserved for printing.

Note that only images which are replaced by the OPI server, and which are raster images, may be subject to color space conversion. All other images remain as they are. Whenever a color space conversion is performed, the source ICC profile associated with each image is used. In the absence of a source profile, the server defaults are used (see 4.1 “ImageServer settings” and 9.1 “ImageServer preferences”).

Color modes for layout images

You may select a color mode for the layout files. You can choose between CMYK, RGB, and CIELab (see Layout Color in 4.1 “ImageServer settings”). By default, OPI sets the Euroscale CMYK color space for layouts, to allow layout applications to print separations.

3.6 How ImageServer applies color matching

The settings for color matching may be different for every printer queue you have defined on your server. The ImageServer CMM (Color Matching Module) is activated by selecting an ICC printer profile for the respective printer queue (see also 4.3 “OPI printer queue settings”).

However, in some specific situations ImageServer performs color matching “behind the scenes”, even though it has not been activated explicitly. These situations are described below (please remember that you must not delete the “ICC-Profiles” volume, because this would disable indirect color matching, which would entirely disable OPI).

The color matching module is active …

ImageServer needs an ICC profile on the output side (printer profile) and an ICC profile on the input side (image source profile) for proper color matching. This means that you need to tag an image profile to every high-resolution image you wish to print with predictable colors, and you have to make sure that your layouts are tagged in case you want to print layouts (see also 5.3 “Tag images with ICC profiles”).

For a general overview of how ICC based color matching works, as well as examples for specific objectives, see B “Colors, color matching, proof printing – basic concepts” and C “ImageServer and color space”.

3.7 How ImageServer finds and replaces image files

Whenever you print a document from a layout application, the OPI software has to locate and find the images that are to replace the low-resolution images you have used for layout purposes. These images, which are required for replacement, may be either high-resolution originals or the layout files again (in case you print your documents with layouts).

If you do not use the layouts at all, but import high-resolution images into your document, there will be no image replacement for printing unless you set the Replace Images option to All for your current printer queue (see also 4.3 “OPI printer queue settings”).


If you want to use OPI from a Windows system, you should always maintain the 3-character file name extension. The extension may be any extension that is supported by Photoshop for Windows!

The finding strategies

ImageServer offers complex finding strategies for image replacement. The software is able to locate images even after you have moved or renamed them – as long as they remain in the same server volume.

Please note that the finding procedures are started automatically during printing. If you want OPI to report missing image files, make sure that the Check Images option is active (default) when setting up the print preferences (see Fig. 4.6 in 4.3 “OPI printer queue settings”). Missing images will then stop the print job. With Check Images switched off, the documents will be printed, but the printouts will show blanks or layout images where the high-resolution images could not be found.


You may use the HELIOS “Error Queue” feature to save and restart print jobs that have produced an error message (see HELIOS Base manual).

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HELIOS Manuals October 14, 2021