gm compare
NAME
| compare - compare two images.
Contents
| Synopsis Description Examples Options Environment Configuration Files Authors Copyright
Synopsis
| compare [ options ... ] reference-image [ options ... ] compare-image [ options ... ]
Description
| 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.
Examples
| 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
| 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).
| -authenticate <string>
| decrypt image with this password
| -colorspace <value>
| the type of colorspace
| -debug <events>
| enable debug printout
| -define <key>{=<value>},...
| add coder/decoder specific options
| -density <width>x<height>
| horizontal and vertical resolution in pixels of the image
| -depth <value>
| depth of the image
| -display <host:display[.screen]>
| specifies the X server to contact
| -endian <type>
| specify endianness (MSB, LSB, or Native) of image
| -file <filename>
| write annotated difference image to file
| -help
| print usage instructions
| -highlight-color <color>
| pixel annotation color
| -highlight-style <style>
| pixel annotation style
| -interlace <type>
| the type of interlacing scheme
| -limit <type> <value>
| Disk, File, Map, Memory, Pixels, or Threads resource limit
| -log <string>
| Specify format for debug log
| -matte
| store matte channel if the image has one
| -maximum-error <limit>
| specifies the maximum amount of total image error
| -monitor
| show progress indication
| -sampling-factor <horizontal_factor>x<vertical_factor>
| chroma subsampling factors
| -size <width>x<height>{+offset}
| width and height of the image
| -type <type>
| the image type
| -verbose
| print detailed information about the image
| -version
| print GraphicsMagick version string
For a more detailed description of each option, see Options, above. GraphicsMagick(1).
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Environment
| COLUMNS
| 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.
| DISPLAY
| X11 display ID (host, display number, and screen in the form hostname:display.screen).
| HOME
| 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.
| MAGICK_CODER_STABILITY
| 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.
| MAGICK_CODER_MODULE_PATH
| 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.
| MAGICK_CONFIGURE_PATH
| 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.
| MAGICK_DEBUG
| Debug options (see -debug for details)
| MAGICK_FILTER_MODULE_PATH
| 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.
| MAGICK_HOME
| 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.
| MAGICK_MMAP_READ
| 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.
| MAGICK_MMAP_WRITE
| 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.
| MAGICK_IO_FSYNC
| 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.
| MAGICK_IOBUF_SIZE
| 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.
| MAGICK_LIMIT_DISK
| Maximum amount of disk space allowed for use by the pixel cache.
| MAGICK_LIMIT_FILES
| Maximum number of open files.
| MAGICK_LIMIT_MAP
| Maximum size of a memory map.
| MAGICK_LIMIT_MEMORY
| Maximum amount of memory to allocate from the heap.
| MAGICK_TMPDIR
| Path to directory where GraphicsMagick should write temporary files. The default is to use the system default, or the location set by TMPDIR.
| TMPDIR
| 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.
| TMP or TEMP
| For Microsoft Windows, the path to the directory where applications should write temporary files. Overridden by MAGICK_TMPDIR if it is set.
| OMP_NUM_THREADS
| 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
| GraphicsMagick uses a number of XML format configuration files:
| colors.mgk
| colors configuration file
      <?xml version="1.0"?>
      <colormap>
        <color name="AliceBlue" red="240" green="248" blue="255"
               compliance="SVG, X11, XPM" />
      </colormap>
| delegates.mgk
| delegates configuration file
| log.mgk
| logging configuration file
      <?xml version="1.0"?>
      <magicklog>
        <log events="None" />
        <log output="stdout" />
        <log filename="Magick-%d.log" />
        <log generations="3" />
        <log limit="2000" />
        <log format="%t %r %u %p %m/%f/%l/%d:\n  %e"  />
      </magicklog>
| modules.mgk
| loadable modules configuration file
      <?xml version="1.0"?>
      <modulemap>
        <module magick="8BIM" name="META" />
      </modulemap>
| type.mgk
| master type (fonts) configuration file
      <?xml version="1.0"?>
      <typemap>
        <include file="type-windows.mgk" />
        <type
          name="AvantGarde-Book"
          fullname="AvantGarde Book"
          family="AvantGarde"
          foundry="URW"
          weight="400"
          style="normal"
          stretch="normal"
          format="type1"
          metrics="/usr/local/share/ghostscript/fonts/a010013l.afm"
          glyphs="/usr/local/share/ghostscript/fonts/a010013l.pfb"
        />
      </typemap>
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Authors
| John Cristy, Bob Friesenhahn, Glenn Randers-Pehrson, William Radcliff, Leonard Rosenthol.
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Copyright
| Copyright (C) 2002 - 2010 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/Copyright.html.
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