[poppler] pdftops creates huge file with simple color background (attached examples)

[William Bader]

tux-yellow and tux-white both convert to a 2549x3299 RGB bitmap that is RunLength compressed and ASCII85 encoded.
The yellow file is larger than the white file because "255 194 14" does not compress as well as "255 255 255".
The original tux image was Flate encoded with /DecodeParms of <</Predictor 15/Columns 512>>
I am not a poppler maintainer, but I think that it should be possible to add an option to do Flate compression.
If you want to look at the code, open poppler/PSOutputDev.cc and search for occurrences of /RunLengthDecode
The "nothing" files are small because they paint the background by drawing a box instead of by copying a bitmapped image.
I think that when a PDF has several images on top of each other, pdftops needs to convert the entire area to a bitmap even if some of the parts were originally drawn with vector commands. The original images have a bitmapped tux over a vector background, but pdftops can't separate them and has to rasterize the entire page.
Regards,
William

To: poppler at lists.freedesktop.org
From: Pierre-Luc.Samuel at ticketmaster.com
Date: Tue, 26 Jan 2016 14:19:17 -0500
Subject: [poppler] pdftops creates huge file with simple color background (attached examples)

Hi poppler team,
 
I have an issue with pdftops version 0.39.0 with conversion of some 
specific templates to postscript.  I have created very simple use cases 
so that you can understand the issue.
 
pdftops tux-white.pdf
pdftops tux-yellow.pdf
ls -al *.ps
-rw-r--r-- 1   2816703 Jan 26 11:53 tux-white.ps
-rw-r--r-- 1  27576263 Jan 26 11:53 tux-yellow.ps
 
The size of the second PS is 27MB, but only the background color has 
changed.  This seems related to the fact that there is an image on the 
template, because if I remove the image, there is no significant size 
difference:
 
pdftops nothing-white.pdf
pdftops nothing-yellow.pdf
ls -al *.ps
-rw-r--r-- 1     11129 Jan 26 10:34 nothing-white.ps
-rw-r--r-- 1     11167 Jan 26 10:34 nothing-yellow.ps
 
Is this a known issue?
 
Thanks!
Pierre-Luc

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