`ps2pdf`: PostScript-to-PDF converter

## Table of contents

> - Overview
> - Usage
> - Options
> - Limitations
> - Known problems
> - Comparison of `ps2pdf` and Acrobat Distiller
> - Acknowledgments

For other information, see the Ghostscript overview.

# Overview

`ps2pdf` is a work-alike for nearly all the functionality (but not the user interface) of Adobe's AcrobatTM 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 in the makefile when Ghostscript was compiled; see the documentation on building Ghostscript for details: this is currently the case on all platforms, in Ghostscript as we distribute it.

# Usage

The usage for `ps2pdf` is

> `ps2pdf` [options] input.[e]ps output.pdf

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

> `ps2pdf` input.[e]ps

which is equivalent to

> `ps2pdf` input.[e]ps input.pdf

There are actually several different `ps2pdf`* scripts: the name `ps2pdf` above refers to any of them.

- `ps2pdf12` will always produce PDF 1.2 output (Acrobat 3-and-later compatible).
- `ps2pdf13` will always produce PDF 1.3 output (Acrobat 4-and-later compatible).
- `ps2pdf14` will always produce PDF 1.4 output (Acrobat 5-and-later compatible).
- `ps2pdf` per se currently produces PDF 1.2 output (Acrobat 3-and-later compatible). However, this may change in the future. If you care about the compatibility level of the output, use `ps2pdf12`, `ps2pdf13`, or `ps2pdf14`, or use the `-dCompatibilityLevel=`1.x switch in the command line.

All of these scripts actually call a script named `ps2pdfwr` or `ps2pdfxx`. The Unix `ps2pdfwr` script assumes that the Ghostscript executable is named `gs`; it is unlikely that you will need to change this. The DOS and MS Windows `ps2pdfxx.bat` script uses the value of the `GSC` environment variable, if defined, as the name of the executable; otherwise the script assumes the executable is named `gswin32c`. So in these environments, if the executable has a different name, you must set `GSC` to the name of the executable.

# Options

The options in the command line may include any switches that may be used with Ghostscript's PostScript and PDF interpreter (see here for a complete list), although almost none of them are useful with `ps2pdf`. The following may be useful:

`-r` resolution
  Sets the resolution for pattern fills and for fonts that must be converted to bitmaps.
`-dProcessColorModel=`device_color_space
  Sets the color space to be used for device-dependent colors in the output. device_color_space may be `/DeviceGray`, `/DeviceRGB`, or `/DeviceCMYK`; the default value is `/DeviceRGB`.

More importantly, options may include `-d` parameter=value or `-s` parameter=string switches for setting "distiller parameters", Adobe's documented parameters for controlling the conversion process. The PostScript `setdistillerparams` and `currentdistillerparams` operators are also recognized when running `ps2pdf`, and provide an equivalent way to set these parameters from within the PostScript input file.

`ps2pdf` also recognizes the following switches:

`-dPDFSETTINGS=`configuration
  Presets the "distiller parameters" to one of four predefined settings:
  - `/screen` selects low-resolution output similar to the Acrobat Distiller "Screen Optimized" setting.
  - `/printer` selects output similar to the Acrobat Distiller "Print Optimized" setting.
  - `/prepress` selects output similar to Acrobat Distiller "Prepress Optimized" setting.
  - `/default` selects output intended to be useful across a wide variety of uses, possibly at the expense of a larger output file.

`ps2pdf` recognizes all of the Acrobat Distiller 4 parameters documented in Adobe Technical Note #5151. The following have their proper effect, except as noted:

> Parameter name |  | Initial value |  | Notes
> `ASCII85EncodePages` |  | false
> `AlwaysEmbed` |  | []
> `AutoFilterColorImages` |  | true |  | 1
> `AutoFilterGrayImages` |  | true |  | 1
> `AutoRotatePages` |  | /None |  |
> `ColorACSImageDict` |  | << >>
> `ColorDownsampleThreshold` |  | 1.5
> `ColorImageDepth` |  | -1
> `ColorImageDict` |  | << >>
> `ColorImageDownsampleType` |  | /Subsample |  | 3
> `ColorImageResolution` |  | 72
> `CompatibilityLevel` |  | 1.3
> `CompressPages` |  | true
> `ConvertCMYKImagesToRGB` |  | true
> `CoreDistVersion` |  | 4000
> `DefaultRenderingIntent` |  | /Default
> `DownsampleColorImages` |  | false
> `DownsampleGrayImages` |  | false
> `DownsampleMonoImages` |  | false
> `EmbedAllFonts` |  | true
> `EncodeColorImages` |  | true
> `EncodeGrayImages` |  | true
> `EncodeMonoImages` |  | true
> `GrayACSImageDict` |  | << >>
> `GrayDownsampleThreshold` |  | 1.5
> `GrayImageDepth` |  | -1
> `GrayImageDict` |  | << >>
> `GrayImageDownsampleType` |  | /Subsample |  | 3
> `GrayImageResolution` |  | 72
> `LockDistillerParams` |  | false
> `LZWEncodePages` |  | false |  | 2
> `MaxSubsetPct` |  | 35
> `MonoDownsampleThreshold` |  | 1.5
> `MonoImageDepth` |  | -1
> `MonoImageDict` |  | << >>
> `MonoImageDownsampleType` |  | /Subsample
> `MonoImageFilter` |  | /CCITTFaxEncode
> `MonoImageResolution` |  | 300
> `NeverEmbed` |  | []
> `OPM` |  | 0
> `PreserveHalftoneInfo` |  | false
> `PreserveOverprintSettings` |  | false
> `TransferFunctionInfo` |  | /Apply |  | 4
> `SubsetFonts` |  | true
> `UCRandBGInfo` |  | /Remove
> `UseFlateCompression` |  | true

(note 1) `AutoFilterxxxImages` doesn't examine the image to decide between JPEG and LZW or Flate compression: it uses JPEG compression if the image has 8 bits per component and does not use an Indexed color space, and LZW or Flate compression otherwise.

(note 2) 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.

(note 3) The `xxxDownsampleType` parameters can also have the value /Bicubic (a Distiller 4 feature), which is currently treated as equivalent to /Average.

(note 4) Currently, the transfer function is always applied. If the corresponding parameter is set to `/Preserve`, the function setting is also copied into the PDF file.

The following are defined and can be set and queried, but do not have any effect:

> Parameter name |  | Initial value |  | Notes
> `AntiAliasColorImages` |  | false
> `AntiAliasGrayImages` |  | false
> `AntiAliasMonoImages` |  | false
> `Binding` |  | /Left
> `CalCMYKProfile` |  | ()
> `CalGrayProfile` |  | ()
> `CalRGBProfile` |  | ()
> `CannotEmbedFontPolicy` |  | /OK
> `ColorConversionStrategy` |  | /LeaveColorUnchanged
> `ConvertImagesToIndexed` |  | false
> `DetectBlends` |  | true
> `DoThumbnails` |  | false
> `EndPage` |  | -1
> `ImageMemory` |  | 500000
> `Optimize` |  | false |  | 5
> `PreserveOPIComments` |  | false
> `sRGBProfile` |  | ()
> `StartPage` |  | 1

(note 5) Optimization (linearization) is implemented with a separate program, `pdfopt` input.pdf output.pdf.

(note 6) Currently, colors for images and shadings are left in the color space specified in the PostScript input, except for `ConvertCMYKImagesToRGB`; the current color in the graphics state (used for fill, stroke, text, and imagemask) is always converted to the color space specified by the current value of `ProcessColorModel`. The intended behavior is the same as for Acrobat Distiller, except that if `ColorConversionStrategy` is set to `/UseDeviceDependentColor`, colors are converted to the color space specified by `ProcessColorModel` rather than always to `/DeviceRGB`.

The following "job control" parameters are recognized, but have no effect:

> Parameter name |  | Initial value
> `AutoPositionEPSFiles` |  | false
> `CreateJobTicket` |  | false
> `EmitDSCWarnings` |  | false
> `ParseDSCComments` |  | false
> `ParseDSCCommentsForDocInfo` |  | false
> `PreserveCopyPage` |  | false
> `PreserveEPSInfo` |  | false
> `UsePrologue` |  | false

# Limitations

`ps2pdf` will sometimes convert text to high-resolution bitmapped fonts rather than to embedded outline fonts. Currently, this will always occur when the PostScript file uses CID-keyed or double-byte fonts, when the input file uses `kshow`, or in some cases if it uses fonts with non-standard encodings; it may occur in other cases as well.

The PDF output always represents the colors of text and graphics in DeviceGray or DeviceRGB color space (or DeviceCMYK if the `ProcessColorModel` parameter has been set to `/DeviceCMYK`); all other color spaces are converted to these. However, for images, it will retain the original color space for DeviceGray, DeviceRGB, DeviceCMYK, certain CIEBased spaces, and Indexed spaces based on these.

`ps2pdf` will sometimes convert PostScript constructs to lower-level ones, even if a higher-level construct is available. For example, if the PostScript file uses `charpath` to set a clipping path consisting of text, `ps2pdf` will write the clipping path as a path in the PDF file, rather than as text, even though PDF is able to express clipping with text. This is only a performance issue, and will be improved incrementally over time.

`ps2pdf` ignores the PDF 1.3 (Acrobat 4.x) pdfmarks related to document content structure: `StRoleMap`, `StClassMap`, `StPNE`, `StBookmarkRoot`, `StPush`, `StPop`, `StPopAll`, `StBMC`, `StBDC`, `EMC`, `StOBJ`, `StAttr`, `StStore`, `StRetrieve`, `NamespacePush`, `NamespacePop`, and `NI`. While this causes some structural information to be omitted from the output file, the displayed and printed output are normally not affected.

`ps2pdf` currently has only very limited support for PDF 1.4. It writes out the blend mode, constant alpha, and text knockout graphics state parameters, and it handles images with soft masks, but it does not handle transparency groups, or soft masks in the graphics state. (Note that there is no standard way to specify any of these things in PostScript, so these statements only apply when the input file is already a PDF 1.4 file.)

# Known problems

Distiller parameters should only be saved by `save` and restored by `restore`, but they are also saved by `gsave` and restored by `grestore`.

Changing the value of the `CompressPages` parameter after any marks have been made on the page may cause a crash.

If you select the `pdfwrite` driver from the command line (`-sDEVICE=pdfwrite`), rather than using one of the `ps2pdf` scripts, the output may contain embedded fonts that are lacking some required information and that Acrobat Reader will not accept.

If the input file downloads Type 1 fonts incrementally, the output file may contain embedded fonts with some information missing from the FontDescriptor, which may crash Acrobat Reader 4 or produce incorrect character spacing.

# Comparison of `ps2pdf` and Acrobat Distiller

According to users, the greatest benefit of `ps2pdf` is that it is more robust than Acrobat Distiller: it will process complex and difficult PostScript files that Acrobat Distiller is not able to handle.

For certain documents, `ps2pdf` is much faster than Adobe Distiller, and may be suitable for run-time conversions. George White, a heavy user of `ps2pdf`, 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.

On the other hand, there are some documents for which `ps2pdf` may be much slower than Acrobat Distiller. Caveat user.

`ps2pdf` usually produces output that is comparable in size to the output of Acrobat Distiller; however, it sometimes produces much larger output, especially if the input file involves pattern fills.

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.

# 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.

Thanks to Martin Hosken of SIL International <http://www.sil.org> for help with testing `ps2pdf` with a wide variety of international fonts.

Copyright © 1996, 2000 Aladdin Enterprises. All rights reserved.

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

Ghostscript version 6.50, 2 December 2000