bashpngbatch-processing

How to convert multiple postscript files into PNGs using Ghostscript

I will be processing hundreds of postscript files and converting them into PNG files with Ghostscript, so I am trying to find a way to batch process them in one command.

When doing this manually I simply do

gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -GraphicsAlphaBits=4 -sOutputFile=output.png input.ps

And this works fine. But it's not practical to be doing this for hundreds of files, so I am trying to find a way to input all files within a folder, ending in _rss.ps, into Ghostscript to convert to PNGs.

When I use

#!/bin/bash
for i in *_rss.ps ; do echo "gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -GraphicsAlphaBits=4 -sOutputFile=${i/_rss.ps/_rss.png} $i" ; done

It gives the exact result I need

gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -dGraphicsAlphaBits=4 -sOutputFile=32532q_rss.png 32532q_rss.ps
gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -dGraphicsAlphaBits=4 -sOutputFile=4323_rss.png 4323_rss.ps
gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -dGraphicsAlphaBits=4 -sOutputFile=54735_rss.png 54735_rss.ps
gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -dGraphicsAlphaBits=4 -sOutputFile=JF290489_rss.png JF290489_rss.ps

but when I remove echo and the quotation marks it gives the following error

GPL Ghostscript 9.25 (2018-09-13)
Copyright (C) 2018 Artifex Software, Inc.  All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Error: /syntaxerror in (binary token, type=137)
Operand stack:

Execution stack:
   %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   false   1   %stopped_push   2047   1   3   %oparray_pop   2046   1   3   %oparray_pop   2026   1   3   %oparray_pop   1884   1   3   %oparray_pop   --nostringval--   %errorexec_pop   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push
Dictionary stack:
   --dict:953/1684(ro)(G)--   --dict:0/20(G)--   --dict:77/200(L)--
Current allocation mode is local
GPL Ghostscript 9.25: Unrecoverable error, exit code 1

Can anyone advise me on what I am doing wrong, or an alternative way to do this?

Solution

  • Thanks for all the suggestions, I really appreciate it.

    The command I posted does now work even though nothing has been changed - I literally copied and pasted it to test and it worked that time, and still does! Perhaps because I made sure it used Ghostscript 10.04.0 rather than an older version, which was pointed out to me, but as far as I can tell they don't differ in these commands.

    Some people pointed out the -d before GraphicsAlphaBits=4 - I ran commands both with and without this and both work

    If anyone is interested, the working script is:

    #!/bin/bash
for i in *_rss.ps ; do gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -dGraphicsAlphaBits=4 -sOutputFile=${i/_rss.ps/_rss.png} $i ; done

    And gives output to stdout:

    GPL Ghostscript 10.04.0 (2024-09-18)
Copyright (C) 2024 Artifex Software, Inc.  All rights reserved.
This software is supplied under the GNU AGPLv3 and comes with NO WARRANTY:
see the file COPYING for details.
Loading NimbusSans-Regular font from %rom%Resource/Font/NimbusSans-Regular... 3502688 2144812 2783288 1486048 2 done.

    As well as producing the PNG files.

    To test:

    #!/bin/bash
for i in *_rss.ps ; do echo "gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -dGraphicsAlphaBits=4 -sOutputFile=${i/_rss.ps/_rss.png} $i" ; done

    and this gives a series of:

    gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r900 -dGraphicsAlphaBits=4 -sOutputFile=prefix_rss.png prefix_rss.ps

    Thanks everyone!