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April 10, 2001 -- Artifex® is pleased to announce the release of GhostscriptTM 7.0. Ghostscript is well known as a leader in PostScript, PDF, and PCL interpreter technologies. With the release of Ghostscript 7.0, Ghostscript now boasts the following added features and functions:

PDF 1.4 transparency

We believe the future of software for the printing industry is PDF. Adobe Illustrator is one of the premier graphic arts composition applications. Historically Adobe Illustrator has used PostScript as the default archiving format for printing. That changed with the release of Adobe Illustrator 9. Adobe Illustrator 9's default archiving format for printing is now PDF 1.4. Adobe made this change to take advantage of the newly implemented alpha-channel transparency feature in PDF 1.4. Forcing PostScript into accepting files with transparency is a force-fit at best, resulting in files that are up to 10X to 100X the size of a corresponding PDF 1.4 file.

The Ghostscript 7.0 release brings PDF 1.4 rendering capability to the leading independent PDF and PostScript implementation.

These features bring compatibility with applications that generate PDF 1.4 files, including Adobe Illustrator 9. Ghostscript 7.0's next generation imaging model includes full alpha transparency and compositing, the full complement of PDF 1.4 blend modes, support for isolated and non-isolated groups, soft masks, and even support for dual alpha channels needed for knockout groups (one channel each for shape and opacity).

Compositing page elements in PDF brings a number of advantages to users. Elements can be kept separate until the last possible moment, without having to composite them all in a graphics-only program such as PhotoShop. Full resolution PDF files can be much smaller, keeping RIP times to a minimum. The rich palette of blending and compositing options gives the greatest flexibility and power to graphic designers.

Ghostscript 7.0 contains the first independent implementation of PDF 1.4 pixel operations. The new pixel compositing engine, suitable for integration in interactive applications, is available separately for licensing.

Renders PDF 1.4 imaging model, including:

  • Full alpha transparency
  • All PDF 1.4 blend modes Isolated and non-isolated groups
  • Soft masks
  • Separate opacity and shape alpha channels for knockout groups

    ICC based color space support

PDF 1.3 and later allows color values to be represented in "ICCBased" color space. This allows PDF files to specify the colors without needing to convert to some other device independent color space such as "CalRGB" or "Lab", simplifying the creation of PDF files. Also, ICCBased color spaces can be used to represent calibrated 4 component CMYK colors, where use of CalRGB or Lab color space would require discarding part of the original color information.

When the ICCBased color space is used, the color profile is embedded in the PDF file. The format of the profile is defined by the International Color Consortium (ICC). The ICC specification is an evolving standard. The ICCBased color spaces supported in PDF 1.3 and later are based on version 3.3 of the ICC specification. Earlier versions of the ICC specification are also supported.

PDF 1.3 and later supports only the following profile types:

  • deviceClass
  • icSigInputClass (‘‘scnr'')
  • icSigDisplayClass (‘‘mntr'')
  • icSigOutputClass (‘‘prtr'')
  • icSigColorSpaceClass (‘‘spac'')

    (this terminology comes from the ICC specification).

Since the ICCBased color space is being used for the specification of a source color space, only the "to CIE" (AToB in ICC parlance) profile information is used; the "from CIE" (BToA) information is ignored when present. More detailed information on PDF ICCBased color space can be found in the "Portable Document Format Reference Manual Version 1.3" in section 7.12.7.