pdfidiff(1) pdfidiff(1)
NAME
pdfidiff - compares two PDF files and write differences to a third file
file.
SYNOPSIS
pdfidiff [-h(elp)] [-f fuzz_dist] [-g(hostscript)] [-m mode] [-o(pti-
mize)] [-q(uiet)] [-r resolution] [-s(ingle_threaded)] oldfile newfile
deltafile
DESCRIPTION
pdfidiff reads in any two PDF files readable by poppler (or
ghostscript) and write out an image-based "delta" file that represents
the differences between the two files. This is accomplished by using
the pdftocairo (or gs), imagdiff, img2pdf, and tempname utilities.
OPTIONS
-h Print help and quit.
-g Use ghostscript (gs) instead of poppler (pdftocairo) as the PDF
rendering engine.
-f fuzz_dist
When performing a grayscale difference analysis, any pixel val-
ues within the distance specified by -f option are considered
equal. This option has no effect on a color difference analy-
sis. The default value is 1.
-m mode
Set of the mode of the difference analysis. At present, five
modes are available, as described in the MODES section. The
default mode is 2.
-o Use opt-pdf to minimize the filesize of intermediate PNG files
before assembling the final PDF file.
-q Cause pdfidiff to silence the progress information normally
printed during operation.
-r resolution
Use the specified resolution (in DPI) when converting from PDF
to intermediate PNG. The default value is 300.
-s The pdfidiff 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.
MODES
1 Grayscale: In this mode, both input files are converted to
grayscale PNG files. Any pixels that are darker (when comparing
old to new) are highlighted in BLUE, and any pixels that are
brighter are highlighted in RED. [On a B&W drawing with a white
background, this results in additions being highlighted in BLUE,
and subtractions being highlighted in RED.]
2 Grayscale (lightened): This works much like the Grayscale anal-
ysis of mode 1, except that all unchanged pixels are shifted
halfway towards white. This makes it easier to identify changes
on files where the background is predominantly white.
3 Grayscale (darkened): This works much like the Grayscale analy-
sis of mode 1, except that all unchanged pixels are shifted
halfway towards black. This makes it easier to identify changes
on files where the background is predominantly black.
4 Color: Here, the differences between the two files are computed
on a per-RED, per-GREEN, and per-BLUE basis and are shifted and
scaled such that unchanged pixels will show up as 50% gray.
5 Color (stretched): Again, differences between the two files are
computed on a per-channel and are shifted that unchanged pixels
will show up as 50% gray, but here the scaling is maximimized to
emphasize differences.
NOTES
The pdfidiff utility uses pdftocairo or gs to convert both input files
into a series of PNG image files. These files are then compared using
imagdiff, and the resulting image "deltas" are reassemblied into a
final PDF file using img2pdf.
CAVEATS
Because the input files are converted from PDF to PNG and are manipu-
lated as bitmaps, the final PDF output will not contains any searchable
string information, even if the input files did. If you need to com-
pare the text found in two different PDF files, you may have better
luck with an alternate tool such as diffpdf or pdf-diff.
SEE ALSO
gs(1), img2pdf(1), parallel(1), imagdiff(1), diffpdf(1), pdf-diff(1),
pdftocairo(1)
COPYRIGHT
Copyright (C) 2018-2021 by Brian Lindholm. This program is free soft-
ware; 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 MER-
CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
littleutils 2021 Mar 28 pdfidiff(1)
littleutils 1.2.5 - Generated Thu Nov 4 13:04:21 CDT 2021