Ghostscript outputs blank pdf

Question

I'm using following command in PHP to convert a PDF with RBG colors to CMYK colors:

$input  = PDF_DIR . 'input.pdf';
$output = PDF_DIR . 'output.pdf'

exec("'gs'
      '-sDEVICE=pdfwrite'
      '-dUseCIEColor'
      '-sProcessColorModel=DeviceCMYK'
      '-sColorConversionStrategy=CMYK'
      '-sColorConversionStrategyForImages=CMYK'
      '-sOutputFile=$output'
      '$input'
");

I am using Ghostscript version 8.71.

gs -v
GPL Ghostscript 8.71 (2010-02-10)
Copyright (C) 2010 Artifex Software, Inc.  All rights reserved.

Somehow the result is always an empty pdf file. Does anyone know what I'm doing wrong?

Thanks in advance for any answers, Cheers!

Some references:

user_701996 · Answer

In addition to what Sami says above (which is excellent advice, you need to see the back channel output) you should also upgrade, 8.71 is quite old.

Ghostscript outputs blank pdf

2 Answers