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NAME
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compare - compare two images.
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Contents
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Synopsis
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compare [ options ... ] reference-image
[ options ... ] compare-image
[ options ... ]
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Description
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compare compares two similar images using a specified statistical
method (see -metric) and/or by writing a difference image
(-file), with the altered pixels annotated using a specified
method (see -highlight-style) and color (see
-highlight-color). Reference-image is the original
image and compare-image is the (possibly) altered version, which
should have the same dimensions as reference-image.
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Examples
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To compare two images using Mean Square Error (MSE) statistical analysis
use:
compare -metric mse original.miff compare.miff
To create an annotated difference image use:
compare -algorithm annotate -highlight-color purple -file diff.miff original.miff compare.miff
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Options
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Options are processed in command line order. Any option you specify on
the command line remains in effect only for the image that follows. All
options are reset to their default values after each image is read.
For a more detailed description of each option, see
Options, above.
GraphicsMagick(1).
| decrypt image with this password |
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-debug <events>
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| add coder/decoder specific options |
| horizontal and vertical resolution in pixels of the image |
| specifies the X server to contact |
| specify endianness (MSB or LSB) of output image |
| write annotated difference image to file |
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-help
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| the type of interlacing scheme |
| Disk, File, Map, Memory, or Pixels resource limit |
| Specify format for debug log |
| store matte channel if the image has one |
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-monitor
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| chroma subsampling factors |
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-size <width>x<height>{+offset}
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| width and height of the image |
| print detailed information about the image |
| print GraphicsMagick version string |
For a more detailed description of each option, see
Options, above.
GraphicsMagick(1).
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Environment
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COLUMNS
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| Output screen width. Used when formatting text for the screen. Many
Unix systems keep this shell variable up to date, but it may need to be
explicitly exported in order for GraphicsMagick to see it. |
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DISPLAY
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| X11 display ID (host, display number, and screen in the form
hostname:display.screen). |
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HOME
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| Location of user's home directory. GraphicsMagick searches for
configuration files in $HOME/.magick if the directory exists. See
MAGICK_CODER_MODULE_PATH, MAGICK_CONFIGURE_PATH, and
MAGICK_FILTER_MODULE_PATH if more flexibility is needed. |
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MAGICK_CODER_STABILITY
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| The minimum coder stability level before it will be used. The
available levels are PRIMARY, STABLE, and UNSTABLE.
The default minimum level is UNSTABLE, which means that all
available coders will be used. The purpose of this option is to reduce
the security exposure (or apparent complexity) due to the huge number of
formats supported. Coders at the PRIMARY level are commonly used
formats with very well maintained implementations. Coders at the
STABLE level are reasonably well maintained but represent less used
formats. Coders at the UNSTABLE level either have weak
implementations, the file format itself is weak, or the probability the
coder will be needed is vanishingly small. |
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MAGICK_CODER_MODULE_PATH
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| Search path to use when searching for image format coder modules.
This path allows the user to arbitrarily extend the image formats
supported by GraphicsMagick by adding loadable modules to an arbitrary
location rather than copying them into the GraphicsMagick installation
directory. The formatting of the search path is similar to operating
system search paths (i.e. colon delimited for Unix, and semi-colon
delimited for Microsoft Windows). This user specified search path is used
before trying the default search path. |
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MAGICK_CONFIGURE_PATH
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| Search path to use when searching for configuration (.mgk) files.
The formatting of the search path is similar to operating system search
paths (i.e. colon delimited for Unix, and semi-colon delimited for
Microsoft Windows). This user specified search path is used before trying
the default search path. |
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MAGICK_DEBUG
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| Debug options (see -debug for details) |
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MAGICK_FILTER_MODULE_PATH
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| Search path to use when searching for filter process modules
(invoked via -process). This path allows the user to arbitrarily
extend GraphicsMagick's image processing functionality by adding loadable
modules to an arbitrary location rather than copying them into the
GraphicsMagick installation directory. The formatting of the search path
is similar to operating system search paths (i.e. colon delimited for
Unix, and semi-colon delimited for Microsoft Windows). This user
specified search path is used before trying the default search path. |
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MAGICK_HOME
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| Path to top of GraphicsMagick installation directory. Only observed
by "uninstalled" builds of GraphicsMagick which do not have their location
hard-coded or set by an installer. |
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MAGICK_MMAP_READ
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| If MAGICK_MMAP_READ is set to TRUE, GraphicsMagick
will attempt to memory-map the input file for reading. This usually
substantially improves read performance if the file has recently been
read. However, testing shows that performance may be reduced for files
accessed for the first time via a network since some operating systems
failed to do read-ahead over network mounts for memory mapped files. |
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MAGICK_MMAP_WRITE
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| If MAGICK_MMAP_WRITE is set to TRUE, GraphicsMagick
will attempt to memory-map the output file for writing. This is an
experimental feature (which is currently broken). Write performance is
usually somewhat worse when using this approach rather than the default
one. |
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MAGICK_IO_FSYNC
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| If MAGICK_IO_FSYNC is set to TRUE, then GraphicsMagick
will request that the output file is fully flushed and synchronized to
disk when it is closed. This incurs a performance penalty, but has the
benefit that if the power fails or the system crashes, the file should be
valid on disk. If image files are referenced from a database, then this
option helps assure that the files referenced by the database are
valid. |
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MAGICK_IOBUF_SIZE
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| The amount of I/O buffering (in bytes) to use when reading and
writing encoded files. The default is 16384, which is observed to work
well for many cases. The best value for a local filesystem is usually the
the native filesystem block size (e.g. 4096, 8192, or even 131,072 for
ZFS) in order to minimize the number of physical disk I/O operations.
I/O performance to files accessed over a network may benefit
significantly by tuning this option. Larger values are not necessarily
better (they may be slower!), and there is rarely any benefit from using
values larger than 32768. Use convert's -verbose option in order
to evaluate read and write rates in pixels per second while keeping in
mind that the operating system will try to cache files in RAM. |
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MAGICK_LIMIT_DISK
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| Maximum amount of disk space allowed for use by the pixel cache. |
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MAGICK_LIMIT_FILES
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| Maximum number of open files. |
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MAGICK_LIMIT_MAP
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| Maximum size of a memory map. |
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MAGICK_LIMIT_MEMORY
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| Maximum amount of memory to allocate from the heap. |
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MAGICK_TMPDIR
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| Path to directory where GraphicsMagick should write temporary
files. The default is to use the system default, or the location set by
TMPDIR. |
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TMPDIR
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| For POSIX-compatible systems (Unix-compatible), the path to the
directory where all applications should write temporary files.
Overridden by MAGICK_TMPDIR if it is set. |
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TMP or TEMP
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| For Microsoft Windows, the path to the directory where applications
should write temporary files. Overridden by MAGICK_TMPDIR if it
is set. |
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OMP_NUM_THREADS
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| As per the OpenMP standard, this specifies the number of threads to
use in parallel regions. Some compilers default the number of threads to
use to the number of processor cores available while others default to
just one thread. See the OpenMP specification for other standard
adjustments and your compiler's manual for vendor-specific settings. |
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Configuration Files
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Authors
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John Cristy,
Bob Friesenhahn,
Glenn Randers-Pehrson,
William Radcliff,
Leonard Rosenthol.
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Copyright
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Copyright (C) 2002 - 2008 GraphicsMagick Group, an organization
dedicated to making software imaging solutions freely available.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files
("GraphicsMagick"), to deal in GraphicsMagick without restriction,
including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of GraphicsMagick,
and to permit persons to whom GraphicsMagick is furnished to do so,
subject to the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of GraphicsMagick.
The software is provided "as is", without warranty of any kind,
express or implied, including but not limited to the warranties of
merchantability, fitness for a particular purpose and noninfringement.
In no event shall GraphicsMagick Group be liable for any claim, damages
or other liability, whether in an action of contract, tort or otherwise,
arising from, out of or in connection with GraphicsMagick or the use or
other dealings in GraphicsMagick.
Except as contained in this notice, the name of the GraphicsMagick
Group shall not be used in advertising or otherwise to promote the sale,
use or other dealings in GraphicsMagick without prior written
authorization from the GraphicsMagick Group.
Additional copyrights and licenses apply to this software. You should
have received a copy of Copyright.txt with this package, which describes
additional copyrights and licenses which apply to this software;
otherwise see http://www.graphicsmagick.org/www/Copyright.html.
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