Image viewer

Attention

🚧 Under Construction - There might be incompatible changes (particularly in the CLI options and configuration) between minor versions of version zero!

If you want to use the viewer in a project while it’s still on version zero, ensure you pin the dependency to a specific minor version e.g >=0.4,<0.5.

On this note, you probably also want to switch to the specific documentation for the version you’re using (somewhere at the lower left corner of this page).

The package includes a standalone in-terminal image viewer based on the library.

The image viewer is started from the command line using either the term-image command (only works if the Python scripts directory is on PATH) or python -m term_image.
*Take note of the differences.

Image sources

The viewer accepts the following kinds of sources:

  • A path to an image file on a local filesystem.

  • A path to a directory on a local filesystem.

  • An Image URL.

Any other thing given as a source is simply reported as invalid.

Modes

The viewer can be used in two modes:

  1. CLI mode

    In this mode, images are directly printed to standard output. It is used when

    • output is not a terminal (even if --tui is specified)

    • there is only a single image source

    • the --cli option is specified

  2. TUI mode

    In this mode, a Terminal/Text-based User Interface is launched, within which images and directories can be browsed and viewed in different ways. It is used when

    • there is at least one non-empty directory source

    • there are multiple image sources

    • the --tui option is specified

Usage

Run term-image with the --help option to see the usage info and help text.
All command-line arguments and options are described there.

Note that some options are only applicable to a specific mode. If used with the other mode, they’re simply ignored.

Some options have a [N] (where N is a number) behind their description, it indicates that the option has a footnote attached.
All footnotes are at the bottom of the help text.

Render Styles

See Render Styles.

By default, the best style supported by the active terminal is automatically detected. A particular render style can be specified using the style config option or the -S | --style command-line option.

If the specified render style is graphics-based and not supported, an error notification is emitted and the process exits with code 1 (FAILURE, see the description below).
If the specified render style is text-based and not [fully] supported, a warning notification is emitted but execution still proceeds with the style.

The --force-style command-line option can be used to bypass style support checks and force the usage of any style whether it’s supported or not.

Cell Ratio

The cell ratio is taken into consideration when setting image sizes for text-based render styles, in order to preserve the aspect ratio of images drawn to the terminal.

This value is determined by the config option cell ratio OR either of the command-line options -C | --cell-ratio or --auto-cell-ratio.
The command-line options are mutually exclusive and override the config option.
By default (i.e without changing the config option value or specifying either command-line option), term-image tries to determine the value from the active terminal which works on most mordern terminal emulators (currently supported on UNIX-like platforms only).
This is probably the best choice, except the terminal emulator or platform doesn’t support this feature.
If term-image is unable to determine this value automatically, it falls back to 0.5, which is a reasonable value in most cases.
In case auto cell ratio is not supported and the fallback value does not give expected results, a different value can be specified using the config or command-line option.

Attention

If using auto cell ratio and the active terminal is not the controlling terminal of the term-image process (e.g output is redirected to another terminal), ensure no process that might read input (e.g a shell) is currently running in the active terminal, as such a process might interfere with determining the cell ratio on some terminal emulators (e.g VTE-based ones).

For instance, the sleep command can be executed if a shell is currently running in the active terminal.

Notifications

Notifications are event reports meant to be brought to the immediate knowledge of the user.
Notifications have two possible destinations:
  • Standard output/error stream: This is used while the TUI is not launched.

  • TUI notification bar: This is used while the TUI is launched.

Notifications sent to the TUI’s notification bar automatically disappear after 5 seconds.

Logging

Logs are more detailed event reports meant for troubleshooting and debugging purporses.

Logs are written to a file on a local filesystem. The default log file is ~/.term_image/term_image.log but a different file can be specified:

  • for all sessions, using the log file config option

  • per session, using the --log-file command-line option

A log entry has the following format:

(<pid>) (<date> <time>) <process>: <thread>: [<level>] <module>: <function>: <message>
  • pid: The process ID of the term-image session.

  • date and time: Current system date and time in the format %Y-%m-%d %H:%M:%S,<ms>, where <ms> is in milliseconds.

  • process and thread: The names of the python process and thread that produced the log record.

    • Only present when the logging level is set to DEBUG (either by --debug or --log-level=DEBUG).

  • level: The level of the log entry, this indicates it’s importance.

  • module: The package sub-module from which it originated.

  • function: The function from which it originated.

    • Only present when running on Python 3.8+ and logging level is set to DEBUG (either by --debug or --log-level=DEBUG).

  • message: The actual report describing the event that occured.

Note

  • Certain logs and some extra info are only provided when logging level is set to DEBUG.

  • Log files are appended to, so it’s safe use the same file for multiple sessions.

  • Log files are rotated upon reaching a size of 1MiB.

    • Only the current and immediate previous log file are kept.

  • The Process ID of the term-image instance preceeds every log entry, so this can be used to distinguish and track logs from different sessions running simultaneously while using the same log file.

Exit Codes

term-image returns the following exit codes with the specified meanings:

  • 0 (SUCESS): Exited normally and successfully.

  • 1 (FAILURE): Exited due to an unhandled exception or a non-specific error.

  • 2 (INVALID_ARG): Exited due to an invalid command-line argument value or option combination.

  • 3 (INTERRUPTED): The program recieved an interrupt signal i.e SIGINT.

  • 4 (NO_VALID_SOURCE): Exited due to lack of any valid source.

Known Issues

  1. The TUI is not supported on Windows

  2. Drawing of images and animations doesn’t work completely well with Python for windows (tested in Windows Terminal and MinTTY). See here for details.

    In the viewer’s CLI mode, use the --h-allow option to specify a horizontal allowance.

  3. Some animations with the kitty render style within the Kitty terminal emulator might be glitchy at the moment. See here for details.

Planned Features

In no particular order:

  • Performance improvements

  • STDIN source

  • Open image in external viewer

  • Pattern-based file and directory exclusion

  • Minimum and maximum file size

  • Optionally following/skipping symlinks

  • Distinguished color for symlinked entries in the list view

  • Full grid view [TUI]

  • Grid cells for directory entries [TUI]

  • CLI grid view

  • Interactive CLI mode

  • Slideshow

  • Zoom/Pan [TUI], Rotate, Flip/Mirror

  • Sorting options

  • Search in iist view

  • Filter in list and grid views

  • Alpha backaground adjustment per image

  • Frame duration adjustment per animated image

  • Copy:

    • Image data

    • File/Directory name

    • Full path

    • Parent directory path

  • Theme customization

  • Configuration menu

  • Also check the library’s Planned Features since the viewer is based on it.

  • etc…