The Show internal command can be used to:

  • Display selected image files in the standalone image viewer
  • Display a slideshow of the contents of the current folder
  • View and manipulate installed viewer plugins (third-party libraries that can extend the image handling abilities of Opus)
  • Dynamically adjust the size of thumbnails displayed in the current file display
  • Execute the internal commands of the standalone image viewer (allowing you to configure the viewer toolbar and hotkeys)

Command Arguments:

Argument Type Possible values Description

(no argument)



Opens the standalone image viewer to display selected files.

Example: Show



(no value)

Used to automatically populate the "next / previous" list in the viewer with other files visible in the folder tab which launched the command.

Use AUTOFILELIST on its own, without LISTSIBLINGS, to make a command with similar behavior to launching the viewer by double-clicking a file. Specifically, it makes the command respect the Generate next/previous list (when opened via double-click) option on the Standalone Viewer page in Preferences, even when not triggered by a double-click. If the option is off then AUTOFILELIST on its own may have no effect.

If you combine AUTOFILELIST and LISTSIBLINGS together, the command will always populate the "next / previous" list, even if the Preferences option is off, unless more than one file is selected. (If two or more files are selected, and you run the command on them, then just those files will be in the "next / previous" list.)

The "next / previous" list generated by AUTOFILELIST (when the Preferences option is on, or when combined with LISTSIBLINGS) will usually be the same as that generated by LISTSIBLINGS on its own. The two differ in situations where what's visible in the folder tab does not correspond to a real folder on disk. If the folder tab has a filter applied, or is showing something like Find Results or a mode like Flat View, then AUTOFILELIST gets you a list which corresponds to that filtered or multi-directory view; on the other hand, LISTSIBLINGS (on its own) gets you a list of files from the same directory as the file you start with, which may be files that are not displayed in the folder tab at all.




Specifies the file or folder to show. If a folder is specified, all files directly below it will be queued to the viewer's "next / previous" list. If you don't provide a file or folder on the command line, all selected files from the folder tab the command was launched from will be used, if applicable. Remember to enclose paths in quotes if they contain spaces.

Since FILE is the default argument, you don't need to explicitly use its name. Both examples below do the same thing:

Example: Show "C:\Pictures\Mum & Dad.jpg"
Example: Show FILE="C:\Pictures\Mum & Dad.jpg"

The FILE argument can also be used with VIEWPANECMD=open to open a particular file in the lister's viewer pane.

Example: Show "C:\Cats\Best Cat.jpg" VIEWPANECMD=open



(no value)

Opens the image viewer in full-screen mode.

Example: Show FULLSCREEN



(no value)

When used with commands which generate a list of items (see dynamic buttons), the HEADING argument adds a small heading at the start of the list. The heading will be hidden when the list is empty. Headings only happen for commands which potentially generate multiple items at the same level as the button itself.

When HEADING is used by itself, without specifying a text value, the main button's label text is used for the heading.


<heading text>

You can specify the heading text if you want it to be different to the button's label.

Example: Show THUMBNAILSIZE=list HEADING="Thumb Size"



(no value)

The viewer which opens will be linked to the lister which ran the command. The viewer tracks the lister's file selection, similar to a detached preview pane. When a file is clicked in the lister, it will be loaded into the viewer.

Example: Show LISTERLINK

If Preferences or other arguments specify re-use of an existing viewer, one will only be re-used if it was also opened with the LISTERLINK argument and came from the same Lister. Similarly, requests to open viewers without LISTERLINK will not re-use viewers opened with it.

This argument is for use on lister toolbars (etc.) when opening a new viewer. See VIEWERCMD=listerlink, below, if you wish to link or unlink a viewer which is already open.


Closes all standalone viewers currently linked to the Lister which runs the command.

Example: Show LISTERLINK=close


Opens a new linked viewer, if the Lister does not have one already, and closes all the Lister's linked viewers otherwise.

Example: Show LISTERLINK=toggle



(no value)

When LISTSIBLINGS is used on its own, without AUTOFILELIST, it automatically populates the "next / previous" list in the viewer with other files from the same directory as the specified file (or single selected file).

If neither LISTSIBLINGS nor AUTOFILELIST are specified, or if the command is run against multiple selected files, only the specified or selected files will be included in the viewer's "next / previous" list.

See the description of AUTOFILELIST for what happens when both are specified, and the differences between the two.




(no value)

Triggers the generation of thumbnail images for all files in the source folder, including those that are currently out-of-view.




<plugin name>

Forces the use of the specified plugin to display the files. Without this, Opus will automatically determine the best plugin to use (or, for a format that can be handled internally, no plugin will be used).

The <plugin name> can be the either the name of the plugin DLL (including the .dll extension) or the "pretty name" of the plugin. Note that this command can't force a plugin to view a file it can't handle.

This argument is also used in conjunction with PLUGINDISABLE to enable or disable the specified plugin.

Example: Show PLUGIN "Animated GIF"



<plugin name>

Displays the About dialog for the specified plugin. The <plugin name> can be the either the name of the plugin DLL (including the .dll extension) or the "pretty name" of the plugin.

Example: Show PLUGINABOUT text.dll



<plugin name>

Displays the configuration dialog for the specified plugin (if it has one).

Example: Show PLUGINCONFIG dcrawrap.dll



(no value)

Toggles the enable state of the specified plugin. If the plugin is currently enabled it will be disabled, and vice versa. The plugin must be specified using the PLUGIN argument.

Example: Show PLUGINDISABLE PLUGIN gifanim.dll


Enables the plugin specified with the PLUGIN argument.

Example: Show PLUGINDISABLE=enable PLUGIN text.dll


Disables the plugin specified with the PLUGIN argument.

Example: Show PLUGIN audiotags.dll PLUGINDISABLE disable


It is not necessary to specify "toggle", since it is the default if neither "enable" nor "disable" are specified, but you can if you want to be more explicit.

Example: Show PLUGIN="audiotags.dll" PLUGINDISABLE=toggle

Note that when a PLUGINDISABLE button is a toggle, the button will appear active (e.g. checked or highlighted) when the plugin is disabled. As with most commands, you can add @toggle:invert on a new line at the top of the command sequence to reverse this.


Show PLUGIN="wma.dll" PLUGINDISABLE=toggle



(no value)

Displays a dynamic list of your installed viewer plugins (acts as a dynamic button). The generated list contains a sub-menu for each viewer plugin, with commands to enable/disable, configure and show information about the plugin.

Example: Show PLUGINLIST



(no value)

Displays the Viewer / Viewer Plugins page in Preferences, which lets you see and manage your installed viewer plugins.





Overrides the default positioning of the standalone viewer, and opens its window at the specified coordinates. This could be used, for example, to always display the viewer on a particular monitor.

Example: Show POS 1920,0




Overrides the default size of the standalone viewer.

Example: Show POS 1920,0 SIZE 960,1080



(no value)

Initiates a slideshow of images. If any files are currently selected in the source file display, only those images will be shown in the slideshow - otherwise, all image files in the current folder will be displayed. Use with the LISTSIBLINGS argument to always include all files in the folder, irrespective of how many are currently selected.

You can adjust the speed of the slideshow, and choose whether the order should be linear or random, from the Slideshow page in Preferences.





Sets the size of thumbnails in the active Lister to the specified size in pixels. This overrides the global thumbnail size set in the File Display Modes / Thumbnails page in Preferences.

Example: Show THUMBNAILSIZE 192


Sets the width and height of thumbnails separately. This lets you have non-square thumbnail sizes if desired.

Example: Show THUMBNAILSIZE 92,64


Adjusts the size of thumbnails in the active Lister by the specified delta value. You must specify either a leading + or - to make this a relative size change.

Example: Show THUMBNAILSIZE +32

<change w>,<change h>

Adjusts both the width and height of thumbnails by the specified deltas.

Example: Show THUMBNAILSIZE +16,+24


Applies the size change to only the left (or top) file display in a dual-display Lister.

Example: Show THUMBNAILSIZE left,128


Applies the size change to only the right (or bottom) file display.

Example: Show THUMBNAILSIZE +64,right


Applies the size change to only the source file display.

Example: Show THUMBNAILSIZE source,64,80


Applies the size change to only the destination file display.

Example: Show THUMBNAILSIZE dest,256


Applies the size change to both visible file displays in a dual-display Lister, but only the active folder tabs.

Example: Show THUMBNAILSIZE both,+32


Applies the size change to all file displays in the Lister, including both sides of a dual-display Lister and all folder tabs. This is the default behaviour.

Example: Show THUMBNAILSIZE all,+32


Resets the thumbnail size to the value set in Preferences.

Example: Show THUMBNAILSIZE all,reset


Generates dynamic buttons that provide a number of thumbnail size options, intelligently chosen to suit your system DPI settings.

Example: Show THUMBNAILSIZE=list



(no value)

Forces the re-use of an existing viewer window - a new window will never be opened if there is an existing viewer currently open. This overrides the Reuse existing viewer window option on the Standalone Viewer page in Preferences.



Prevents the re-use of an existing viewer window - a new window will always be opened.

Example: Show USEEXISTING=no


Avoids switching to another virtual desktop - will only re-use a window on the same desktop. This overrides the Avoid switching desktops option.

Example: Show USEEXISTING=yes,avoid


Does not avoid switching to another virtual desktop.

Example: Show USEEXISTING=yes,noavoid




Only for use in the standalone viewer, this command forms the basis of the default viewer toolbar, context menu and hotkeys. These commands can also be used from scripts that run within the context of the viewer.


Toggle the Hide Alpha Channel option on and off.

Example: Show VIEWERCMD=alpha


(Opus 13.4.2 and above.) Toggle the Keep On Top option on and off. This makes the viewer always on-top relative to other normal windows.

Example: Show VIEWERCMD=alwaysontop

If Preferences or Customize are opened, the viewer will reset to normal to avoid the dialogs opening behind it. Full-screen viewers are inherently on-top when active, regardless of this setting.

You can also specify on or off to ensure the viewer is in a particular mode instead of toggling.

Example: Show VIEWERCMD=alwaysontop,on


Override or reset the viewer's background color. This only affects viewers and plugins which support it, and is useful for checking images that use transparency against various background colors. The change is temporary (not saved to your configuration) and only affects the viewer the command is run in.

If no color is specified, the background is reset to the color from Preferences.

Example: Show VIEWERCMD=backcol

Otherwise, a color should be specified in either #RRGGBB hex or RRR,GGG,BBB decimal format:

Example: Show VIEWERCMD=backcol,#FFFFFF
Example: Show VIEWERCMD=backcol,127,127,127

If you need a button or hotkey which toggles a color override on each push, edit the items in the default Viewer toolbar's View / Background Color menu to see how it's done.


Closes the standalone viewer window.

Example: Show VIEWERCMD=close


Displays a FAYT-style command bar at the bottom of the viewer window, which lets you type in an ad-hoc command to run in the context of the viewer.

Example: Show VIEWERCMD=cmdbar


Copies the currently selected region of the image to the clipboard.

Example: Show VIEWERCMD=copy


Prompts for a new filename to copy the currently viewed file to.

Example: Show VIEWERCMD=copyto


Crops the image to the currently selected region. The file on disk is not modified unless the image is saved.

Example: Show VIEWERCMD=crop


Cuts the currently viewed file to the clipboard. If you then perform a paste in a Lister the viewed file will be moved.

Example: Show VIEWERCMD=cut


Deletes the currently viewed file (after prompting for confirmation, by default).

Example: Show VIEWERCMD=delete

The main difference between using this command and the actual Delete command is that the viewer will move to the next file after the current one has been deleted.

The additional options can be specified:

  • close automatically closes the viewer after deleting the image
  • noadvance stops the viewer moving onto the next image after deleting the image

You may also specify one or more of the following Delete command arguments: shift, force, quiet, norecycle, recycle, or secure (or secure=n for n passes).

Any additional options or Delete command arguments must be included in a comma separated list without any extra spaces:

Example: Show VIEWERCMD=delete,quiet,secure=2

If no additional arguments are given, the shift argument is implicit, to maintain the old default behavior. If you only wish to disable the shift argument, use noshift:

Example: Show VIEWERCMD=delete,noshift


Lets you trigger certain mouse actions from an OnViewerEvent script event. For example, when the script event is triggered to tell you the user clicked the left mouse button, you could trigger scrolling or expand mode depending on where on the window the mouse was clicked.

The default behavior is to scroll; use the "select" keyword to trigger selection mode, and "expand" to trigger expand/scroll mode.

By default the command assumes the left mouse button was used to trigger the event - use the "rclick" keyword for the right mouse button, and "mclick" keyword for the middle mouse button.

You can also provide the coordinates of the click by passing "pos:x,y" on the command line - if not provided, the current mouse position is assumed.

Example: Show VIEWERCMD=dragsel,expand,mclick,pos:100,100


Goes back to view the first file in the list.

Example: Show VIEWERCMD=first


Flips the currently viewed image. The file on disk is not modified unless the image is saved. Use with horiz to flip horizontally or vert to flip vertically.

Example: Show VIEWERCMD=flip,horiz


Turns the standalone viewer's picture frame option on or off. This only affects viewers and plugins which support it (most image types, but not things like Office or PDF documents). The change affects all open viewer windows and is saved to your configuration.

The frame is toggled by default.

Example: Show VIEWERCMD=frame

You can also specify "on" or "off" to explicitly turn the frame on or off.

Example: Show VIEWERCMD=frame,on


Turns full-screen mode on and off. By default, it will toggle the setting, but you can also explicitly turn it on or off.

Example: Show VIEWERCMD=fullscreen
Example: Show VIEWERCMD=fullscreen,on
Example: Show VIEWERCMD=fullscreen,off


Adjust the gamma value of the image display. The adjustment value can be one of the following:

+<value>increase gamma by <value>
-<value>decrease gamma by <value>
<value>set absolute gamma to value
0-<value>set absolute negative gamma value
resetreset gamma to default value

Example: Show VIEWERCMD=gamma,+1
Example: Show VIEWERCMD=gamma,reset


Go to a specified file in the list. Must be used with a value indicating the image, where 0 is the first image, 1 is the second and so on. This command can also be used to jump forwards or backwards a specific number of files, by specifying a number preceded by + or -.

Example: Show VIEWERCMD=goto,0
Example: Show VIEWERCMD=goto,+10


Displays help about the image viewer.

Example: Show VIEWERCMD=help


Toggles the display in and out of hexadecimal mode.

Example: Show VIEWERCMD=hex


Toggles the image information overlay on and off.

Example: Show VIEWERCMD=info


Go to the last file in the list.

Example: Show VIEWERCMD=last


Link or unlink the viewer from the lister that opened it. When a lister and viewer are linked, selecting a file in the lister will display it in the viewer, making a standalone viewer like a detached preview pane.

If listerlink is specified on its own, it will toggle the link (assuming the lister still exists). You can also specify toggle to be more explicit, or on or off to turn linking on or off without toggling.

Example: Show VIEWERCMD=listerlink
Example: Show VIEWERCMD=listerlink,off

This is for running via viewer toolbars (etc.) to change the link state of an existing viewer. There is also a standalone LISTERLINK argument (above) which can be used to open new viewers from a lister and link them as soon as they open.


This keyword is used to control image marking. It has many different functions, which are accessed by combining it with the following keywords:

(no sub-keyword)Toggle mark state of current image (same as the toggle keyword).
browseBrowse marked pictures (opens the marked pictures collection in a new tab).
clearClear all marks.
exchangeExchange the current image for the previously marked image (unmarks the previous one and marks this one in its place).
firstJump to the first marked image.
lastJump to the last marked image.
nextJump to the next marked image.
nohighlightPrevents a button being highlighted when the condition it describes is true (e.g. when an image is marked, stops a mark,toggle button from being highlighted). Use with on, off, toggle and view.
offUnmarks the current image.
onMarks the current image.
prevJump to the previously marked image.
returnReturn from a jump to the image you were previously viewing (e.g. after mark,first to jump to the first marked image, mark,return would put you back where you were).
toggleToggle mark state of current image.
viewToggle the marked pane on and off.

Example: Show VIEWERCMD=mark,toggle,nohighlight
Example: Show VIEWERCMD=mark,view


Use this in conjunction with next and prev to mark the previous image before moving onto the next (or previous) one.

Example: Show VIEWERCMD=next,markfirst


Toggles the embedded metadata panel on or off, and controls its width. Combine with the following keywords:

<width>Specify the width of the metadata panel in pixels.
growWhen opening the metadata panel, the viewer window will grow as much as possible to accommodate it. When closing the panel, provided the window has not been manually resized, its original width will be restored.
nofocusPrevents the metadata editor from gaining input focus when it opens.
offTurns the metadata panel off.
onTurns the metadata panel on.
toggleToggles the metadata panel on and off.

Example: Show VIEWERCMD=meta,toggle,grow,400


Save the width of the current viewer window as the new minimum width. When new viewers open they won't automatically size themselves narrower than this width.

Example: Show VIEWERCMD=minwidth


Assuming a multi-monitor system, moves the viewer to the next monitor. Most useful with full-screen viewers.

Example: Show VIEWERCMD=monitornext


Move the viewer to the previous monitor.

Example: Show VIEWERCMD=monitorprev


Prompts for a new filename to move the currently viewed file to.

Example: Show VIEWERCMD=moveto


Go to and view the next file in the list. You can combine this with markfirst to mark the current image first.

Example: Show VIEWERCMD=next


Generates a list of the subsequent files in the image list (acts as a dynamic button - designed for use on the drop-down attached to the Next button).

Example: Show VIEWERCMD=nextlist


Hides this button when the viewer is not in full-screen mode. You can combine this with any other keyword.

Example: Show VIEWERCMD=delete,notfullscreen


Hides this button unless the viewer is in full-screen mode. You can combine this with any other keyword.

Example: Show VIEWERCMD=close,onlyfullscreen


Open and view a new file. By default this will prompt for the file to open, but you can provide a filename on the command line (e.g. from a script).

Example: Show VIEWERCMD=open
Example: Show VIEWERCMD="open,c:\my pictures\image.jpg"


Displays the About dialog for the current viewer plugin.

Example: Show VIEWERCMD=pluginabout


Displays the configuration dialog for the current viewer plugin (if it provides one).

Example: Show VIEWERCMD=plugincfg


Trigger a command provided by the current viewer plugin (if it provides any). The command is specified as a number where 0 means the first command, 1 means the second and so on.

Example: Show VIEWERCMD=plugincmd,0


Generates a list of the commands provided by the current viewer plugin (if it provides any). This acts as a dynamic button.

Example: Show VIEWERCMD=plugincmds


Go to and view the previous file in the list. You can combine this with markfirst to mark the current image first.

Example: Show VIEWERCMD=prev,markfirst


Generates a list of the previous files in the image list (acts as a dynamic button - designed for use on the drop-down attached to the Previous button).

Example: Show VIEWERCMD=prevlist


Print the currently viewed file.

Example: Show VIEWERCMD=print


Refresh the currently viewed file. The file will be reloaded from disk.

Example: Show VIEWERCMD=refresh


Reselect the previous selection. This lets you easily crop more than one image to the same area (i.e. select a region, crop and save this image, move to the next image, reselect the previous region, crop and save, …).

Example: Show VIEWERCMD=reselect


Undoes the previous crop operation.

Example: Show VIEWERCMD=restore


Rotate the display of the current image. The file on disk is not modified unless you save the image. The amount to rotate by can be specified as follows:

+<value>rotate clockwise by <value> degrees
-<value>rotate anti-clockwise by <value> degrees
<value>set rotation to an absolute value
resetreset the rotation

Example: Show VIEWERCMD=rotate,+90


Save any changes you have made to the current image. Use with the quiet option to replace the existing file silently. This command is unavailable if the image is not in one of the formats that Opus is able to save (currently PNG, JPG, BMP and GIF) - in that case, you can use saveas to save the image in one of those formats.

Example: Show VIEWERCMD=save,quiet


Prompts for a new filename to save the image to. The Save Picture dialog also lets you choose the image format to save in. You can optionally provide a filename to save to on the command line (e.g. from a script).

Example: Show VIEWERCMD=saveas
Example: Show VIEWERCMD="saveas,c:\my pictures\image.png"


Scrolls the current image. You must specify either horiz or vert to indicate the dimension you want to scroll, combined with another keyword to indicate how far to scroll. The keywords are:

bottomScroll to the bottom (vertical) or far right (horizontal).
downScroll down (vertical) or right (horizontal).
horizScroll horizontally.
pagedownScroll down a page (vertical) or right a page (horizontal).
pageupScroll up a page (vertical) or left a page (horizontal).
topScroll to the top (vertical) or far left (horizontal).
upScroll up (vertical) or left (horizontal).
vertScroll vertically.
centerScroll to the center. Can optionally be combined with horiz or vert.

Example: Show VIEWERCMD=scroll,vert,pagedown


Fixes the aspect ratio of the selection marquee. You can specify an aspect ratio (16:9, 3/2, etc), or reset to remove the restriction.

Example: Show VIEWERCMD=selaspect,16:9
Example: Show VIEWERCMD=selaspect,reset


Select the entire image.

Example: Show VIEWERCMD=selectall


Select the currently displayed file in the folder tab the viewer was launched from.

Example: Show VIEWERCMD=selectfile


Toggle the display of the shortcut bar on and off.

Example: Show VIEWERCMD=shortcutbar


Toggle slideshow mode on and off.

Example: Show VIEWERCMD=slideshow

You can also turn it on or off explicitly, regardless of its current state:

Example: Show VIEWERCMD=slideshow,on
Example: Show VIEWERCMD=slideshow,off


Toggle the status bar on and off.

Example: Show VIEWERCMD=statusbar


Toggle display of the toolbar on and off.

Example: Show VIEWERCMD=toolbar


Sets the currently displayed image as your Windows desktop wallpaper. By default the wallpaper will be set to center mode, but you can specify a mode by providing an additional keyword:

centerThe image will be centered on the desktop with a solid color fill surrounding it (this is the default).
fillThe image will be expanded or shrunk to fill the desktop (may leave black bars at the top and bottom or sides, to preserve the aspect ratio).
fitThe image will be expanded or shrunk to fill the desktop (the top and bottom or sides of the image may be cropped to preserve the aspect ratio).
spanThe image will be spanned across multiple monitors.
stretchThe image will be stretched to fit the monitor, ignoring its aspect ratio.
tileA small image will be tiled multiple times horizontally and vertically to fit the monitor.

Example: Show VIEWERCMD=wallpaper,span


Adjusts the zoom level of the current image display. You must provide an additional keyword to indicate the desired zoom level:

+zoom in.
-zoom out.
+<value>Zoom in a specified amount (percentage).
-<value>Zoom out a specified amount (percentage).
<value>Zoom to an absolute percentage of the original size.
fitSet zoom mode to "fit to page" - the image will be shrunk to fit the page if it's too large to fit all at once.
growSet zoom mode to "grow to page" - the image will be shrunk to fit if it's larger, and expanded to fill the page if it's smaller.
tileSet zoom mode to "tile" - a small image will be tiled multiple times horizontally and vertically to fill the page.
resetReset the zoom level.

Example: Show VIEWERCMD=zoom,+




Sends commands to the Lister's viewer pane.

Most of the available commands correspond to buttons in the viewer pane's toolbar and context menu, and exist so you can create hotkeys to perform the same actions.


Change the viewer pane's background color, overriding the color specified in Preferences.

This only affects image viewers and plugins which support it, and is useful for checking images that use transparency against various background colors.

If no color is specified, the background is reset to the color from Preferences:

Example: Show VIEWPANECMD=backcol

Otherwise, a color should be specified in either #RRGGBB hex or RRR,GGG,BBB decimal format:

Example: Show VIEWPANECMD=backcol,#FFFFFF


Unload any existing file and clear the viewer pane.

Example: Show VIEWPANECMD=clear


Toggle the picture frame on and off (if supported by the current viewer).

Example: Show VIEWPANECMD=frame


Go to the previews file.

Example: Show VIEWPANECMD=prev


Go to the next file.

Example: Show VIEWPANECMD=next


Open a particular file in the viewer pane.

Example: Show VIEWPANECMD="open,C:\My Image.png"

When using open, you may want to first run Set VIEWPANELOCK=On to prevent the viewer pane from loading other files when they are selected in the file display.

You can also specify the file to open using the FILE argument instead:

Example: Show FILE="C:\Cats\Best Cat.jpg" VIEWPANECMD=open

Finally, Show VIEWPANECMD=open on its own can be used to simply open the viewer pane, although Set VIEWPANE=On or Set VIEWPANE=Toggle are the more standard ways of doing that.


Rotate the image 90 degrees counter-clockwise.

Example: Show VIEWPANECMD=rotateleft


Rotate the image 90 degrees clockwise.

Example: Show VIEWPANECMD=rotateright


Reduce the image, if needed, to fit the available space.

Example: Show VIEWPANECMD=zoomfit


Enlarge or reduce the image to match the available space.

Example: Show VIEWPANECMD=zoomgrow


Increase the zoom amount by one step.

Example: Show VIEWPANECMD=zoomin


Decrease the zoom amount by one step.

Example: Show VIEWPANECMD=zoomout


Show the image at 100% zoom.

Example: Show VIEWPANECMD=zoomreset