pdfquant(1) General Commands Manual pdfquant(1)
NAME
pdfquant - reduce the size of the colormap used by bitmap images
embedded in PDF files.
SYNOPSIS
pdfquant [-h(elp)] [-f(loyd-steinberg)] [-n colors] [-o(ptimize)]
[-q(uiet)] [-s(ingle_threaded)] file...
DESCRIPTION
pdfquant extracts the main bitmap images from one or more PDF files and
writes out new PDF files that contain alternate versions of the bitmaps
with reduced colormaps. This is accomplished using the pdfseparate,
pdfimages, pngquant, img2pdf, and tempname utilities. It is targeted
at PDF files generated by document scanning software.
OPTIONS
-h Print help and quit.
-f Use Floyd-Steinberg dithering instead of ordered dithering.
This significantly improves the appearance of color images, but
also increases the size of the output files substantially.
-n colors
Reduce the number of colors used on each page to the value
specified. Only a number between 2 and 256 can be used, and the
default value is 8.
-o Use opt-pdf to minimize the filesize of intermediate PNG files
(using opt-png) before assembling the final PDF file. This
significantly increases computation time.
-q Cause pdfquant to silence the progress information that is
normally printed during operation.
-s The pdfquant utility will normally utilize GNU parallel (if
present on the system) to perform operations in parallel to
reduce computation time. Using this option will force single-
threaded operation.
CAVEATS
The pdfquant utility only uses the first bitmap image extracted from
each page of the PDF file. It does not extract text or vector
graphics, nor does it utilize any additional bitmaps extracted.
Generally speaking, the only PDF files that contain a single whole-page
bitmap on each page are those generated by document scanning software.
If you use pdfquant on PDF files exported from office suites, CAD
packages, desktop publishing software, etc., you will almost certainly
be disappointed.
Also, if you plan to use pdfquant to convert embedded bitmaps to
strictly black-and-white (not grayscale), the pdfbw4 utility should be
used instead. It yields better results.
SEE ALSO
img2pdf(1), parallel(1), pdfimages(1), pdfseparate(1), pngquant(1),
pdfbw4(1)
COPYRIGHT
Copyright (C) 2021-2026 by Brian Lindholm. This program is free
software; you can use it, redistribute it, and/or modify it under the
terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
littleutils 2026 Jan 01 pdfquant(1)
littleutils 1.4.0 - Generated Wed Feb 18 07:38:11 CST 2026