`ps2pdf`: PostScript-to-PDF converter

## Table of contents

> - Overview
> - Usage
> - Limitations
> - Known problems
> - Benefits of using `ps2pdf`
> - Acknowledgments

For other information, see the Ghostscript overview.

# Overview

`ps2pdf` is a work-alike for the functionality (but not the user interface) of Adobe's Acrobat DistillerTM product: it converts PostScript files to Portable Document Format (PDF) files.

`ps2pdf` is implemented as a very small command script (batch file) that invokes Ghostscript, selecting a special "output device" called `pdfwrite`. In order to use `ps2pdf`, the `pdfwrite` device must be included as a device list when Ghostscript was built; see the documentation on building Ghostscript for details. The `pdfwrite` device is currently included in the makefiles for all platforms.

# Usage

The usage for ps2pdf is

> `ps2pdf input.ps output.pdf`

or, on Unix systems and some versions of Windows NT and OS/2

> `ps2pdf input.ps`

which is equivalent to

> `ps2pdf input.ps input.pdf`

The `ps2pdf` command script assumes that the Ghostscript executable is named `gs`. On DOS and MS Windows where the command-line executable has a different name, you must edit the script `ps2pdf.bat` if the DOS executable is named `gs386`: look for the line that says

> `set PS2PDFGS=gs`

and change it to

> `set PS2PDFGS=gs386`

Note that to run `ps2pdf` on MS Windows, you need the DOS executable: the Windows Program Manager's "`run` command doesn't allow you to run `.bat` files. Alternatively you can run the "console mode" Windows executable by changing the line above to

> `set PS2PDFGS=gswin32c`

# Limitations

The most serious limitation of `ps2pdf` is that text in any font other than the fourteen Adobe base fonts (Courier, Times, and Helvetica families, Symbol, and Zapf Dingbats) is converted to bitmaps. `ps2pdf` also may convert strings to bitmaps if the string is in one of those base fonts but contains a character that uses a non-standard encoding.

`ps2pdf` implements `setdistillerparams`, and recognizes all of the parameters documented in Adobe Technical Note #5151 except for the `ImageDict` parameters, but only a subset have an effect:

> Parameters |  | Effective |  | Ignored
> General |  | `ASCII85EncodePages`, `CompatibilityLevel`, `CompressPages`, `CoreDistVersion`, `LZWEncodePages` (see below), `UseFlateCompression` |  | `AutoRotatePages`, `ImageMemory`, `PreserveHalftoneInfo`, `PreserveOPIComments`, `PreserveOverprintSettings`, `TransferFunctionInfo`, `UCRandBGInfo`
> General image |  | `AutoFilterxxxImages` (see below), `xxxImageDepth`, `xxxImageDownsampleType`, `xxxImageFilter`, `xxxImageResolution`, `DownsamplexxxImages`, `EncodexxxImages`, `MonoImageDict` |  | `AntiAliasxxxImages`, `xxxACSImageDict`, `ColorImageDict`, `GrayImageDict`
> Color image |  | `ConvertCMYKImagesToRGB` |  | `ColorConversionStrategy`, `ConvertImagesToIndexed`

Because of Unisys's threats regarding the Welch patent, `ps2pdf` cannot actually use LZW compression: instead, it treats all requests for LZW compression as calling for `Flate` compression if `UseFlateCompression` is true and `CompatibilityLevel` >= 1.2, and ignores them otherwise.

`AutoFilterxxxImages` doesn't examine the image to decide between JPEG and `LZW/Flate` compression: it always uses `LZW/Flate` compression.

# Known problems

Some PDF files created using `ps2pdf` work with Adobe Acrobat on Unix but fail using the MS Windows version of Acrobat. One error that has been observed using versions of Acrobat reader for Windows is: "There was an error processing a page. A rasterizer error occurred." This error has been observed using both Acrobat version 2.1 and the Alpha 2 release of Adobe Amber. (Adobe may have fixed this problem by now.)

`ps2pdf` does not yet process the new PDF 1.2 (Acrobat 3.x) `BP`, `EP`, `SP`, and `OBJ` and related pdfmarks. If the application uses these pdfmark commands (and few applications do), some material may be lost from the output file.

# Benefits of using `ps2pdf`

Despite the limitations of `ps2pdf`, the class of "suitable" documents is a large one. Many users report that the combination of `ps2pdf` with Acrobat is superior to using a generic PostScript viewer (`psview` or `ghostview`), particularly for documents with many pages where the navigational support in PDF files reduces the overhead involved in navigating conventional PostScript documents.

For certain documents, `ps2pdf` is much faster than Adobe Distiller, and may be suitable for run-time conversions. [George White remarks "I haven't seen a head to head comparison, but Distiller seems slower when running on what should be a faster system (for instance, Distiller on a PPC Mac vs a 25 MHz 68040 NeXT running `ps2pdf`), so I think this is fair -- also, one of Mark Doyle's postings indicated that Distiller was not fast enough for use as a run-time server. In contrast, I find that I can use `ps2pdf` as a post-processor during routine document creation."]

# Acknowledgments

Thanks to George N. White III <aa056@chebucto.ns.ca> of the Ocean Sciences Division of the Bedford Institute of Oceanography in Dartmouth, Nova Scotia for extensive testing of early versions of `ps2pdf`, and for contributing most of this writeup.

Copyright © 1996, 1997, 1998 Aladdin Enterprises. All rights reserved.

This file is part of Aladdin Ghostscript. See the Aladdin Free Public License (the "License") for full details of the terms of using, copying, modifying, and redistributing Aladdin Ghostscript.

Ghostscript version 5.50, 16 September 1998