rot-jpg(1) General Commands Manual rot-jpg(1)
NAME
rot-jpg - losslessly rotate JPEG images by 90, 180, or 270 degrees
SYNOPSIS
rot-jpg [-h(elp)] [-f filelist] [-F(ast)] [-l(eft)] [-p(ipe)]
[-r(ight)] [-t(ouch)] [-T threads] [-u(pside-down)] file...
DESCRIPTION
rot-jpg losslessly rotates JPEG images using the jpegtran utility.
OPTIONS
-h Print help and quit.
-f file_list
Read the names of files to be processed from the specified file
-F Run faster by skipping the opt-jpg post-processing that is
normally performed.
-l Rotate image by 270 degrees clockwise. In other words, turn the
top of the image to the left.
-p Read the names of files to be processed from stdin.
-r Rotate image by 90 degrees clockwise. In other words, turn the
top of the image to the right.
-t Preserve timestamp on modified files.
-T threads
Process up to the specified number of files in parallel. The
default value is half the multi-threading capability of the CPU,
i.e., half the sibling count as listed in /proc/cpuinfo.
-u Rotate image by 180 degrees clockwise. In other words, turn the
image upside-down.
EXAMPLES
Spin a couple of image files to the left:
rot-jpg -l image001.jpg image002.jpg
Spin all images in a directory tree to the right, utilizing half of all
cores: find . -name "*.jpg" -print | rot-jpg -p -r
Fully utilize a quad-core system to spin all images upside-down:
find . -name "*.jpg" -print | rot-jpg -p -T 4 -u
NOTES
If rot-jpg appears to be malfunctioning, try running it in single-
threaded mode by using the -T 1 option. This permits more meaningful
error messages to be printed.
WARNING
The rotation performed by rot-jpg is perfectly lossless if the image
dimensions are an exact multiple of the JPEG iMCU size (usually 8 or 16
pixels), which is normally the case with images coming out of a digital
camera or cell phone. However, if the image is not an exact multiple,
then the extra pixels at the right and/or bottom of the image will be
cropped. See the jpegtran manpage for more details.
SEE ALSO
jpegtran(1), opt-jpg(1)
COPYRIGHT
Copyright (C) 2019-2026 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 rot-jpg(1)
littleutils 1.4.0 - Generated Wed Feb 18 07:43:43 CST 2026