ImageServer G8 User manual (Version 6.0.0)  

G Glossary


Adobe Document Structuring Conventions (ADSC) provide directions for the structuring of PostScript files.

AFP server

Apple file server using the Apple Filing Protocol (AFP).

Alpha channels

The high-order 8 bits of a 32-bit graphics pixel used to manipulate the remaining 24 bits for purposes of coloring or masking. Also called Additional channels.


Bilevel images contain only two colors: black and white. “Lineart” is one example of bilevel images.


Acronym for Bitmap. A simple graphics file format developed by Microsoft for its Windows operating system. BMP files can store graphics from 1-bit (2-color) up to 24-bit (16.7 millions of colors). But since the BMP format does not support any method of compression, images may consume considerable space on your hard drive.


Acronym for Black Point Compensation. A software setting that maps the black point of the source profile to the black point of the destination profile.


Comité Consultatif International Téléphonique et Télégraphique, renamed to ITU-T in 1993. This group specified communication protocols for a particular class of devices (e.g. facsimile devices) and represents specific modes of compression (CCITT Group 3, CCITT Group 4).


The Commission Internationale de l’Eclairage (CIE) is responsible for the definition of color models and the standardization of color descriptions. The Lab color space has been defined by the CIE.


CIELab colors are defined by the L-value for lightness and the coordinates a and b defining the quantitative distance of a color from a reference white point. The Lab color space includes all visible colors and is device independent.

Clipping paths

A clipping path is a mask you can apply to an image if you want to cut out a specific part. The clipping path may be a rectangle or an ellipse; some applications also allow defining an irregular clipping path.


Color printing is based on the CMYK color space. Cyan, Magenta, Yellow, and Black inks are mixed on paper to produce a given color. The definitions of the basic colors Cyan, Magenta, Yellow, and Black are slightly different in Europe (Euroscale), the US (SWOP), and Japan.

Color matching

The process of adjusting or matching colors appropriately to achieve maximum similarity from the gamut of one color space to the other. In practice, the color data delivered by a given device – e.g. a scanner – have to be transformed so that the colors can exactly be reproduced by a second device – e.g. a printer.

Color mode

See: Bilevel, Grayscale, Indexed colors, RGB, CMYK, CIELab, Spot color, Multichannel, Multitones, and YCbCr, YCbCrK.


ColorSync offers a programming interface to a fast computing engine which uses ICC profiles as parameters to perform color transformations between different devices. Apple ColorSync 2 has been co-developed by Apple Computer and Linotype-Hell.


Compress is a lossless compression mode that can be used for different color modes and file formats. It collects repetitive patterns in a table and saves references to this table whenever possible.


See: Compress, CCITT, Flate, JPEG, JBIG2, PackBits RLE, Wavelet, and Zip.

DCS 1, DCS 2

The Desktop Color Separations file format (DCS) has been developed by Quark, Inc. and is based on the standard EPSF format. DCS 1 images are composed of five files, namely the preview and the EPSF separation plates for Cyan, Magenta, Yellow, and Black. DCS 2 is a single-file format that includes the preview and the separation plate information.


Discrete Cosine Transformation is a technique for representing waveform data as a weighted sum of cosines. DCT is commonly used for data compression, as in JPEG. This usage of DCT results in lossy compression. DCT itself does not lose data; rather, data compression technologies that rely on DCT approximate some of the coefficients to reduce the amount of data.

DeviceLink profile

The International Color Consortium (ICC) has defined ICC profiles which describe the color characteristics of graphics devices (such as scanners, monitors, and printers) and of abstract color spaces (such as CIELab D50, CIELab D65, and CIELuv). Additionally, the ICC has defined DeviceLink ICC profiles, which describe mappings from one particular color space to another particular color space, e.g. from an offset press CMYK color space to a gravure press CMYK color space. Many DeviceLink ICC profiles maintain special characteristics of the black channel and fulfill special conditions for color sums according to the drying capabilities of a particular printing process.


DeviceN is the PostScript 3 device-dependent instance of a multi-component color space. This type of color space allows for the specification of color components other than the standard set of three (RGB) or four (CMYK) color components usually used by most applications.


The process of transforming a high-resolution image into a low-resolution image.


See: Resolution


The Encapsulated PostScript File (EPSF) format is meant for pictures that are to be used in different applications or on different platforms. EPSF files contain a text file that lists the PostScript instructions necessary to create the picture and, in addition to that, may contain a PICT preview of the image. If an EPSF file is created by – or exported from – an illustration or DTP application (e.g. InDesign, QuarkXPress) this file contains object-based PostScript instructions and can only be placed in other documents; it cannot be reloaded or edited again. This is only possible, if you are using an image processing application like Photoshop which is able to create raster-based EPSF files. Please note that EPSF files and PC-EPSF files (for Windows computers) are not identical. PC-EPSF files contain compressed TIFF previews (instead of PICT previews) and, therefore, behave differently in specific situations.


Euroscale defines the European ink set for the process colors Cyan, Magenta, Yellow, and Black.

File format

See: BMP, DCS 1, DCS 2, EPSF, ICS, JPEG, JPEG 2000, JBIG2, PDF, Photoshop, PICT, PNG, Scitex CT, TIFF.


Flate (also called Zip) is a compression method that works well on images with large areas of single colors or repeating patterns. The Flate method is lossless, which means it does not remove data to reduce file size and so does not affect an image’s quality.

Gamut, gamut mapping

The gamut is the range of color that a given device can produce. Gamut mapping means re-defining the colors of a given device so that its gamut becomes (approximately) identical to that of a second device.


GFX describes the internal HELIOS data structure. It may contain color space, compression method, plate information, etc. of each object in a file.


Grayscale images are a generalization of Bilevel images. They contain black and white and different shades of gray.

Home directory

Private directory provided for each UNIX user. The home directory is the current directory as soon as you login to a server via Terminal.

ICC, ICC profiles

The International Color Consortium (ICC) is a group of vendors who defined the ICC-profile format. This format is a cross-platform specification which allows third party vendors to develop profile tools and applications supporting the standard. The founding members of this consortium include: Adobe Systems Inc., Agfa-Gevaert N.V., Apple Computer, Inc., Eastman Kodak Company, FOGRA (Honorary), Microsoft Corporation, Silicon Graphics, Inc., Sun Microsystems, Inc., and Taligent, Inc. These companies have committed themselves to fully support this specification in their operating systems, platforms and applications. (See also Profiles.)


ICS is a proprietary format that has been created by Linotype-Hell. It is a modification of the EPSF/DCS 1 format.

Indexed colors

Images with indexed colors use colors from a given RGB color map. Every pixel of such an image contains a reference to a specific color in the map.


JPEG is a file format and – at the same time – a mode of compression. Images are compressed by replacing several similar colors by one color only. Thus, some color data is lost and cannot be recreated when the files are opened again. JPEG has been developed by the Joint Photographic Experts Group (JPEG).

JPEG 2000

A potential successor to JPEG with better compression and multiresolution images. JPEG 2000 gives reasonable quality down to 0.1 bits/pixel (JPEG quality drops dramatically below about 0.4 bits/pixel).


A compression standard for lossless bilevel image coding. Its lossless algorithm features compatible progressive coding and sequential coding – the image is unaltered after compression and decompression. JBIG2 has been developed by the Joint Bi-level Image Experts Group.


A Multichannel image contains different color modes – e.g. CMYK colors and several spot colors – at the same time.


Colorized Grayscale

PackBits RLE

Apple Mac OS compression, mainly used for PICT files.


The Portable Document Format (PDF) is an Adobe Acrobat file format that has been created for application independent file exchange. With the Adobe Reader software – which can be downloaded from the Adobe website – you may read and print any given PDF document.


Photoshop is the native Adobe Photoshop application specific file format.


The PICT file format is the native classic Mac OS image format.


Acronym for Portable Network Graphics. Bitmapped graphics format conforming to the “Portable Network Graphics Tenth Specification” (Version 1.0). The PNG format is similar to GIF (Graphics Interchange Format). However, it does not use patented data compression and is license-free. The World Wide Web consortium approved it as a standard to replace GIF. Most browsers support the PNG format.


PostScript Printer Description (PPD), is a file format developed by Adobe Systems, Inc. PPD files contain information enabling software to produce the best results possible for each type of designated printer.


A profile is a device description. It contains information about how a given device (scanner, monitor or printer) mixes and reproduces colors.

Rendering intent

The approach taken when a Color Management Module (CMM) maps or translates the colors of an image to the color gamut of a destination device. Each profile supports different rendering intents. Changing the rendering intent may lead to a different output result, even though you did not change the profile.


The dots per inch (dpi) value of an image indicates its resolution. The resolution of a given device (e.g. scanner, printer) defines its resolution capacity. Very clear and sharp images require input/output devices with a high resolution (300 dpi or more). Monitor resolutions usually range from 72 to 200 dpi.


Screens and monitors produce colors by means of Red, Green and Blue light (RGB). The light intensities make up a given color. Scanners also work with RGB colors. They read the amounts of red, green, and blue light that are reflected from an image (or transmitted if you scan transparent images). RGB images contain three components per pixel, namely a specific amount of red, green, and blue.


A Raster Image Processor (RIP) performs the final calculation of the data which are sent to the output device. The RIP may be either an external unit or part of the output device itself. A PostScript laser printer for example contains its RIP.


Run-Length Encoding (RLE) is a mode of compression that saves repetitive patterns only once and adds the number of repetitions. RLE is a lossless compression.

Root directory

The top-most directory on a UNIX computer is called “root” directory. If you are logged in as “root”, you can access all other directories and subdirectories on the system.

Scitex CT

Scitex Continuous Tone (CT) is a proprietary image file format that has been developed by Scitex Corporation, Ltd.


A spooler is a set of programs which manage print jobs. A spooler acts as a buffer for the files that have been sent to an output device.

Spot color

A spot color is an exactly defined full tone color. Spot colors are printed on their own separation plates when separations are specified.


The Specifications for Web Offset Publications (SWOP) include US standards for color separation and color printing.


The protocols and services included in Apple’s network architecture. The access to the EtherShare file server and print server use TCP/IP.


The Tagged Image File Format (TIFF) is a standard graphics file format for files that are to be exchanged among several applications and environments, including Mac, DOS/Windows, and UNIX.


A lossy compression method of an image. Compression is achieved by converting the image into a set of mathematical expressions. The JPEG 2000 image format uses wavelet compression.


The YCbCr color mode is used by the television industry for digital videos. There are transformation tables that allow transforming YCbCr into RGB and vice versa. YCbCrK is a JPEG-based format that has been developed by Adobe.


A lossless file compression method, which is based on the DEFLATE algorithm for compression (see Flate).

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HELIOS Manuals October 14, 2021