NAME
    cv - a fast gtk+ image viewer loosely modeled after XV

SYNOPSIS
       cv

       cv directory

       cv path...

       cv -g <glob expression...>

       find .. -print0 | cv -0r

       cv --sort ...

FEATURES
    CV is supposed to work similar to the venerable XV image viewer, just
    faster. Why faster?

    *   optimized directory scanning algorithm

        The directory scanning in CV uses some tricks that - on most modern
        filesystems - makes it possible to detect filetypes faster than
        stat()'ing every file. This makes CV suitable for directories with
        lots of files (10000+).

        This algorithm is quite unprecise - it doesn't make a difference
        between files, device nodes, symlinks and the like, and filetype
        detection is done using the file extension only.

        On the positive side, it is usually many orders of magnitude faster
        than traditional scanning techniques (good for directories with
        10000 or 100000+ files).

    *   queuing for all time-consuming background tasks

        All tasks, such as unlinking files or generating thumbnails, that
        can be done in the background will be done so - no waiting required,
        even when changing directories.

    *   use of asynchronous I/O

        CV tries to use asynchronous I/O whereever it makes sense, for
        example while scanning directories, waiting for stat data, unlinking
        files or generating thumbnails. This usually decreases scanning
        times for large directories a bit (especially on RAID devices and
        over NFS) and makes CV much more interactive.

    *   fast image loading

        The time span between the user issuing a command and displaying the
        new image should be as small as possible. CV uses optimized
        (especially for JPEG) loading functions and sacrifices some quality
        (e.g no gamma correction, although this might change) to achieve
        this speed.

    *   fast thumbnail creation

        Thumbnail creation uses both CPU and Disk-I/O. CV interleaves both,
        so on modern CPUs, thumbnailing is usually limited by I/O speed.
        Thumbnail creation for JPEGs has been specially optimized and can
        even take advantage of multiple CPUs.

    *   minimum optical clutter

        CV has no menus or other user interface elements that take up a lot
        of screen space (or are useful for beginning users). The schnauzer
        windows can also be somewhat crowded.

        The point of an image viewer is viewing images, not a nice GUI. This
        is similar to XV's behaviour.

    *   efficient (and hard to learn) user interface

        CV uses key combinations. A lot. If you are an experienced XV user,
        you will find most of these keys familiar. If not, CV might be hard
        to use at first, but will be an efficient tool later.

    *   multi-window GUI

        CV doesn't force you to use a specific layout, instead it relies on
        your window manager, thus enabling you to chose whatever layout that
        suits you most.

    *   i18n'ed filename handling throughout

        As long as glib can recognize your filename encoding (either UTF-8
        or locale-specific, depending on the setting of G_BROKEN_FILENAMES)
        and you have the relevant fonts, CV will display your filenames
        correctly.

    *   extensible through plug-ins

        I have weird plug-ins that access remote databases to find a
        directory. This is not likely to be of any use to other people.
        Likewise, others might have weird requirements I cannot dream of.

    *   filename clustering

        Among the standard plug-ins is a filename clustering plug-in, that
        (in case of tens of thousands images in one directory) might be able
        to cluster similar names together.

DESCRIPTION
  THE IMAGE WINDOW
    You can use the following keys in the image window:

     q            quit the program
     <            half the image size
     >            double the image size
     ,            shrink the image by ~9% (opposite of .)
     .            enlarge the image by 10%
     n            reset to normal size
     m            maximize to screensize
     M            maximize to screensize, respecting image aspect
     ctrl-m       toggle maxpect-always mode
     ctrl-sift-m  toggle using current image size as max image size
     u            uncrop
     r            set scaling mode to 'nearest' (fastest)
     s            set scaling mode to 'bilinear' (default)
     t            rotate clockwise 90°
     T            rotate counterclockwise°
     a            apply all rotations loslessly to a jpeg file (using exiftran)
     ctrl-shift-t apply current rotation for future image loads
     ctrl-v       open a new visual schnauzer window for the current dir
     ctrl-c       clone the current image window
     ctrl-e       run an editor ($CV_EDITOR or "gimp") on the current image
     ctrl-p       fire up the print dialog
     ctrl-shift-p same as ctrl-p, but automatically selects "ok"
     escape       cancel a crop action

    And when playing movies, these additional keys are active:

     left         rewind by 10 seconds
     right        forward by 10 seconds
     down         rewind by 60 seconds
     up           forward by 60 seconds
     pg_up        rewind by 600 seconds
     pg_down      forward by 600 seconds
     o            toggle on-screen display
     p            pause/unpause
     escape       stop playing
     9            turn volume down
     0            turn volume up

    Any other keys will be sent to the default schnauzer window, which can
    be toggled on and off by right-clicking into the image window.

    Left-clicking into the image window will let you crop the image (usually
    to zoom into large images that CV scales down).

  THE VISUAL SCHNAUZER
    Any image-loading action in a schnauzer window acts on the
    "last-recently-activated" imagewindow, which currently is simply the
    last image window that received a keypress.

    You can use the following keys in the schnauzer window:

     ctrl-space,
     space        move to and display next image
     ctrl-backspace,
     backspace    move to and display previous image
     ctrl-return,
     return       display selected picture, or enter directory

     cursor keys  move selection
     page-up      move one page up
     page-down    move one page down
     home         move to first file
     end          move to last file

     ctrl-a       select all files
     ctrl-shift-a select all files currently displayed in the schnauzer window
     ctrl-d       delete selected files WITHOUT ASKING AGAIN
     ctrl-g       force generation of thumbnails for the selected files
     ctrl-shift-g remove thumbnails for the selected files
     ctrl-s       rescan current direcory or files updates/deletes etc.
     ctrl-u       update selected (or all) icons if neccessary
     ctrl--       unselected thumbnailed images
     ctrl-+       keep only thumbnailed images, deselect others

     ^            go to parent directory (caret).

     0-9,
     a-z          find the first filename beginning with this letter

    Right-clicking into the schnauzer window displays a pop-up menu with
    additional actions.

   SELECTION
    You can select entries in the Schnauzer in a variety of ways:

    Keyboard
        Moving the cursor with the keyboard will first deselect all files
        and then select the file you moved to.

    Clicking
        Clicking on an entry will select the one you clicked and deselect
        all others.

    Shift-Clicking
        Shift-clicking will toggle the selection on the entry under the
        mouse.

    Dragging
        Dragging will select all entries between the one selected when
        pushing the button and the one selected when releasing the button.
        If you move above or below the schnauzer area while drag-selecting,
        the schnauzer will move up/down one row twice per second. In
        addition, horizontal mouse movement acts as a kind of invisible
        horizontal scrollbar.

    Hint: double-click works while click-selecting
        You can double-click any image while click-selecting to display it
        without stopping the selection process. This will act as if you
        normally double-clicked the image to display it, and will toggle the
        selection twice, resulting in no change.

FILES
    When starting, CV runs the .cvrc file in your $HOME directory as if it
    were a perl script. in that, you will mostly load plug-ins.

    Example:

       system "fping -q -t 10 ether"
         or require "/fs/cv/cvplugin.pl";

    This will load a plug-in, but only if the machine *ether* is reachable
    (supposedly the plug-in is networked in some way :).

ENVIRONMENT VARIABLES
    CV_EDITOR
        The program that gets executed when the user presses "CTRL-e" in the
        Schnauzer or image window. The default is "gimp".

    CV_AUDIO_PLAYER
        EXPERIMENTAL: audio playback is now via mpv, this variable is
        currently ignored.

        Program used to play all sorts of audio (wav, aif, mp3, ogg...),
        default "play". Will be called like "$CV_AUDIO_PLAYER -- <path>".

    CV_MPLAYER
        Program used to play all sorts of video files. Unlike
        "CV_AUDIO_PLAYER", this really must be some version of the "mpv"
        programs, or something that is very command-line compatible to them.

        Note: for video-thumbnailing, mplayer is still used (and hardcoded).

    CV_PRINT_DESTINATION
        The default (perl-style) destination to use in the print dialog.

    CV_TRASHCAN
        When set, must point to a directory where all files that are deleted
        by the "Delete Physically" (ctrl-d) action are moved to (other
        deletion actions still delete!). If unset, files that are deleted
        are really being deleted.

SIGNALS
    Sending CV a SIGUSR1 signal will cause all image viewers to reload the
    currently loaded image. This is useful if you use CV as a viewer for
    changing data - just run it in the background with some path and each
    time the image changes, send it a SIGUSR1.

SECURITY CONSIDERATIONS
    CV uses Pixbuf to load non-JPEG images. Pixbuf is not considered safe
    for this purpose, though (from the gtk-2.2 release notes):

    "While efforts have been made to make gdk-pixbuf robust against invalid
    images, using gdk-pixbuf to load untrusted data is not recommended, due
    to the likelyhood that there are additional problems where an invalid
    image could cause gdk-pixbuf to crash or worse."

BUGS/TODO
     Lots of functionality is missing.

     Pixbuf doesn't always honor G_BROKEN_FILENAMES, so accessing files with
     names incompatible with utf-8 might fail.

     rotate on disk
     lots of ui issues
     save(?)
     preferences

AUTHOR
    Marc Lehmann <cv@plan9.de>.

