==============
perceptualdiff
==============
A program that compares two images using a perceptually based image metric.
.. image:: https://travis-ci.org/myint/perceptualdiff.svg?branch=master
:target: https://travis-ci.org/myint/perceptualdiff
:alt: Build status
.. image:: https://scan.coverity.com/projects/1561/badge.svg
:target: https://scan.coverity.com/projects/1561
:alt: Static analysis status
Copyright (C) 2006-2011 Yangli Hector Yee
Copyright (C) 2011-2016 Steven Myint, Jeff Terrace
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, 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 in the
file ``LICENSE``.
Build Instructions
==================
#. Download CMake from http://www.cmake.org if you do not already have it on
your system.
#. Download FreeImage from https://sourceforge.net/projects/freeimage.
- On OS X with MacPorts: ``port install freeimage``
- On OS X with Brew: ``brew install freeimage``
- On Ubuntu: ``apt-get install libfreeimage-dev``
#. Type::
$ make
#. To specify the install directory, use::
$ make install DESTDIR="/home/me/mydist"
Usage
=====
Command line::
Usage: perceptualdiff image1 image2
Compares image1 and image2 using a perceptually based image metric.
Options:
--verbose Turn on verbose mode
--fov deg Field of view in degrees [0.1, 89.9] (default: 45.0)
--threshold p Number of pixels p below which differences are ignored
--gamma g Value to convert rgb into linear space (default: 2.2)
--luminance l White luminance (default: 100.0 cdm^-2)
--luminance-only Only consider luminance; ignore chroma (color) in the
comparison
--color-factor How much of color to use [0.0, 1.0] (default: 1.0)
--down-sample How many powers of two to down sample the image
(default: 0)
--scale Scale images to match each other's dimensions
--sum-errors Print a sum of the luminance and color differences
--output o Write difference to the file o
--version Print version
Check that perceptualdiff is built with OpenMP support::
$ ./perceptualdiff | grep -i openmp
OpenMP status: enabled
Credits
=======
- Hector Yee, project administrator and originator - hectorgon.blogspot.com.
- Scott Corley, for png file IO code.
- Tobias Sauerwein, for make install, package_source Cmake configuration.
- Cairo Team, for bugfixes.
- Jim Tilander, rewrote the IO to use FreeImage.
- Steven Myint, for OpenMP support and bug fixes.
- Jeff Terrace, for better FreeImage support and new command-line options.
Version History
===============
- 1.0 - Initial distribution
- 1.0.1 - Fixed off by one convolution error and libpng interface to 1.2.8
- 1.0.2 - [jt] Converted the loading and saving routines to use FreeImage
- 1.1 - Added colorfactor and downsample options. Also always output
difference file if requested. Always print out differing pixels even if the
test passes.
- 1.1.1 - Turn off color test in low lighting conditions.
- 1.1.2 - Add OpenMP parallel processing support and fix bugs.
- 1.2 - Add ``--sum-errors``, use more standard option style, and fix bugs.
- 1.3 - Add MSVC compatibility.
- 1.4 - Detect differences due to the alpha channel. This was lost in 1.0.2
when FreeImage was introduced.
- 2.0 - Support usage as a library.
- 2.1 - Allow accessing stats directly when used as a library.
Usage as a library
==================
.. code:: cpp
#include <perceptualdiff/metric.h>
#include <perceptualdiff/rgba_image.h>
int main()
{
const auto a = pdiff::read_from_file("a.png");
const auto b = pdiff::read_from_file("b.png");
const bool same = pdiff::yee_compare(*a, *b);
}
Links
=====
* Coveralls_
.. _`Coveralls`: https://coveralls.io/r/myint/perceptualdiff