Recent changes in Ghostscript

# Changes in the most recent release of Ghostscript

This document is news about the most recent Ghostscript release. For earlier versions, see the history documents:

> History of Ghostscript versions 9.n
> History of Ghostscript versions 8.n
> History of Ghostscript versions 7.n
> History of Ghostscript versions 6.n
> History of Ghostscript versions 5.n
> History of Ghostscript versions 4.n
> History of Ghostscript versions 3.n
> History of Ghostscript versions 2.n
> History of Ghostscript versions 1.n

For other information, see the Ghostscript overview.

## Version 9.04 (2011-08-05)

This is the fourth full release in the stable 9.x series.

This release includes fixes and solutions for a number of serious problems from the earlier 9.x releases and so we strongly encourage those using earlier 9.x releases to upgrade to this new version, to reap the benefits of those fixes.

In addition, those still using Ghostscript 8.71 and earlier should begin migration to 9.x soon since many improvements, features and fixes from the 9.x versions are impractical to back-port to these legacy versions.

Highlights in this release include:

- Transition source base to git source control - not a big deal for most users, but an important change for those develop Ghostscript and GhostPDL.
- This release introduces flexibility for controlling color based upon the graphic object type. In particular, it is now possible to specify unique output ICC profiles and rendering intents for vector graphic, image and tex portions of a document. It is also possible to override source color specifications and use specified ICC profiles and rendering intents for RGB and CMYK vector graphics, images and text portions of a document. Finally, DeviceGray source colors can now easily be specified to map either to K only or composite CMYK when the output device supports CMYK colorants.
- New tiffscaled8 and tiffscaled24 devices. Add new tiffscaled8 and tiffscaled24 devices, copied and modified from tiffscaled. These output greyscale and 24bit rgb instead of tiffscaleds mono output. MinFeatureSize is ignored for these devices as it's meaningless for contone output. Downscaling is also now supported for png16m and pnggray, and a new pngmonod device has been implemented which uses grayscale rendering internally and then downscales/min_feature_sizes/error diffuses to monochrome.
- The PDF interpreter will now try continue interpreting a PDF after encountering an error in a stream. The previous bevahior can be reinstated by passing -dPDFSTOPONERROR to Ghostscript.
- Re-enable x11alpha as the default device on Unix systems, now that compatibility problems between anti-aliased output and transparency are resolved.
- Update libjpeg to version 8c.
- Experimental Text output/extraction device

  The txtwrite device has undergone some development, and now has genuine functionality. It accepts any input format which GhostPDL supports, and uses a combination of methods to try and determine the Unicode values for any text contained in the document.

  The code descends a hierarchy of methods in this process, starting with the most reliable and only falling back to less reliable methods when better methods fail. The current hierarchy is as follows:

  1. ToUnicode CMaps (PostScript or PDF) or GlyphNamesToUnicode tables (PostScript).
  2. Glyph names of the form 'unixxxx'.
  3. Glyph names defined in the Adobe Glyph List document.
  4. Input character code.

  Method 1 is highly reliable, method 4 is a best guess and not terribly reliable, though it will work for many files. It is probably most reliable for PostScript and PCL files.

  The device currently has one parameter 'TextFormat' which controls whether the output is Unicode text reflecting the layout of the original document (-dTextFormat=0) or a format intended for use by developers which includes the Unicode text and some formatting information, such as the size and position of the text, and the font in use (-dTextFormat=1).

  Note that his device does not do OCR (Optical Character Recognition) it is not capable of finding 'text' which is part of an image. However it will recover the 'invisible' text from PDF documents which have been scanned and OCR'ed by Acrobat for searching. Such text has a render mode of 3.

  This is the first release of this code and is very much an alpha release, we expect problems.

  In particular the TextFormat=0 output is likely to be incorrect, and will only work with top-to-bottom left-to-right text. It will probably also be confused by landscape documents printed on portrait media.

  TextFormat=1 should be more reliable, but there may be cases where text is dropped from the output. Text in PostScript documents using charpath is not yet supported for example.

  We do encourage feedback on the state of this device, and would be interested in hearing what kind of output would be useful for developers using TextFormat=1. For now, however, please do not raise bugs through Bugzilla, instead please send feedback to the gs-devel mailing list.

- Experimental Unicode/UTF8 Support on Windows

  This release introduces some experimental build-time optional support for UNICODE pathnames on Windows. Essentially this works by following the model that Linux (and MacOS) have followed for years.

  If this code is enabled, then the way ghostscript handles command lines, registry settings, file accesses and other api calls with top bit set characters in (i.e. codes >= 128) will change. The net benefit of this change is that ghostscript will now be able to cope with accessing files with unicode characters (i.e. codes >= 256) in their pathnames.

  This behaviour is all completely transparent to users, with the exception of those calling the gsapi functions with strings including 'extended ascii' (i.e. characters with codes >= 128 and <= 255). These characters include accented latin characters, such as u + umlaut, a + grave etc. The changes required for code that is affected by this are relatively minor, but as this is a change to the current API, we are announcing it in advance, and inviting comments.

  As of the 9.04 release, the code is disabled. For those who wish to experiment you will need to build Ghostscript from source, and either pass USEUNICODE=1 when you invoke nmake or edit psi/msvc.mak to remove the /DWINDOWS_NO_UNICODE option from CFLAGS.

  WARNING: Our intention, subject to feedback, is to enable this by default in near-future releases (hopefully, the next major release). If you make use of the affected APIs you should be prepared for the change to occur - be aware, however, that the current code is experimental and, depending on the feedback we get, maybe subject to change.

  NOTE: this whole change refers to file paths, command line parameters and so on - it does not imply that we have unilaterally extended Postscript to understand UNICODE.

  More details:

  To give an example, suppose we have a file 'EXAMPLE' we'd like to invoke ghostscript on, where 'EXAMPLE' is actually a string that contains some characters with codes >= 128.

  On Linux (or MacOS X), when ghostscript is called from a shell, e.g.

  gs EXAMPLE

  the command is UTF8 encoded; this means that characters with codes < 128 are left unchanged, and characters >= 128 are encoded into multiple bytes. This encoded string is then passed to the standard 'main' entrypoint in the gs executable.

  Ghostscript proceeds internally without any special handling of these multibyte characters at all. When it comes to access files it therefore passes out the UTF8 encoded strings to the standard OS file handling routines. These routines are designed to take pathnames in UTF8 format, and thus the files are accessed as normal.

  If the Ghostscript executable outputs these (or other) strings to its stdout, the shell again converts the output from UTF8 back to unicode in order to display it.

  The net effect is that the caller can seamlessly pass in unicode filenames, has his fileaccesses work out and gets unicode output without the core of ghostscript ever having to worry about it.

  The code change discussed here endeavours to make Windows follow the same pattern as closely as possible.

  When Windows executables are invoked, they can either be called through an 'ascii' entrypoint (main), or through a unicode ('wide') entrypoint (wmain). The difference is invisible to the caller, except that unicode executables can accept characters >= 256 in their invocations.

  The new code changes ghostscript from being an ascii executable to being a unicode one. The Windows specific outer layer takes the unicode command string and UTF8 encodes it before passing it to the ghostscript core.

  Similarly, the Windows specific filing system calls are updated to accept utf8 encoded strings from the core, and to convert them to unicode before operating on them.

  The Windows gui app (gswin32.exe, NOT gswin32c.exe) is also updated to convert stdin/stdout between unicode and utf8 as appropriate, allowing unicode strings to be copied/pasted to/from other apps.

  All of this should be completely transparent to the user, and no code changes should be required. The one area where changes may be required are where ghostscript is invoked through the gsapi functions.

  Currently, on Linux (and MacOS X) any strings sent over the gsapi are assumed to be utf8 encoded (and thus can represent any Unicode character). On Windows, they are assumed simply to be in extended ASCII (and can therefore represent any character < 256 in the current codepage). With the proposed change, Windows will move to be in step with Linux. No differences will be caused to anyone who only uses chars <= 128, but those people using character codes between 128 and 256 (or indeed wanting to use higher codes) will need to utf8 encode the strings before calling gsapi functions.

  Such encoding/decoding is a very simple process, and code for both directions can be found in psi/dwmain.c, psi/dwmainc.c and psi/dwtext.c.

  Again, we welcome feedback on this feature, in this case problems or suggestions about the implementation can be submitted via Bugzilla but for detailed discussion about the approach for which we opted, it would be more beneficial discuss it (preferably) on our IRC channel #ghostscript on freenode.net, or on the gs-devel mailing list.

For a list of open issues, or to report problems, please visit bugs.ghostscript.com.

### Incompatible changes

Deprecated file "gs/base/errors.h" removed, psi/ierrors.h should be used instead.

The eXternal Fonts (XFonts) functionality, marked as deprecated in 9.02 has now been fully removed.

No other recorded incompatible changes.

### Changelog

See the history file for complete log of changes.

Copyright © 2005-2011 Artifex Software, Inc. All rights reserved.

This software is provided AS-IS with no warranty, either express or implied. This software is distributed under license and may not be copied, modified or distributed except as expressly authorized under the terms of that license. Refer to licensing information at http://www.artifex.com/ or contact Artifex Software, Inc., 7 Mt. Lassen Drive - Suite A-134, San Rafael, CA 94903, U.S.A., +1(415)492-9861, for further information.

Ghostscript version 9.04, 5 August 2011