The vtkdiff tool shall provide means of numerical comparison of different data arrays similar to those available in the numdiff software.

The Visualization Toolkit (VTK) is a C++ library for 3D computer graphics, image processing and visualization. It supports a wide variety of visualization algorithms including: scalar, vector, tensor, texture, and volumetric methods; and advanced modeling techniques such as: implicit modeling, polygon reduction, mesh smoothing, cutting, contouring, and Delaunay triangulation. VTK has an extensive information visualization framework, has a suite of 3D interaction widgets, supports parallel processing, and integrates with various databases on GUI toolkits such as Qt and Tk.

G'MIC is a full-featured framework for digital image processing. It provides several user interfaces to convert / manipulate / filter / visualize generic image datasets, ranging from 1D scalar signals to 3D+t sequences of multi-spectral volumetric images, hence including 2D color images.

DCMTK is a collection of libraries and applications implementing large parts the DICOM standard. It includes software for examining, constructing and converting DICOM image files, handling offline media, sending and receiving images over a network connection, as well as demonstrative image storage and worklist servers.

ITK-SNAP is a tool for segmenting anatomical structures in medical images. It provides an automatic active contour segmentation pipeline, along with supporting a manual segmentation toolbox. ITK-SNAP has a full-featured UI aimed at clinical researchers.

The Visualization Toolkit (VTK) is a C++ library for 3D computer graphics, image processing and visualization. It supports a wide variety of visualization algorithms including: scalar, vector, tensor, texture, and volumetric methods; and advanced modeling techniques such as: implicit modeling, polygon reduction, mesh smoothing, cutting, contouring, and Delaunay triangulation. VTK has an extensive information visualization framework, has a suite of 3D interaction widgets, supports parallel processing, and integrates with various databases on GUI toolkits such as Qt and Tk.

Chafa is a command-line utility that converts all kinds of images, including animated GIFs, into ANSI/Unicode character output that can be displayed in a terminal.

gpicview is a lightweight GTK+ 2.x based image viewer. It is the default image viewer on LXDE desktop environment.

Viewnior is an image viewer program. Created to be simple, fast and elegant. Its minimalistic interface provides more screenspace for your images. Among its features are:

1. Fullscreen & Slideshow

2. Rotate, flip, crop, save, delete images

3. Animation support

4. Browse only selected images

5. Navigation window

6. Set image as wallpaper (Gnome 2, Gnome 3, XFCE, LXDE, FluxBox, Nitrogen)

7. Simple interface

8. EXIF and IPTC metadata

9. Configurable mouse actions

PIXterm shows images directly in your terminal, recreating the pixels through a combination of ANSI character background color and the unicode lower half block element. It supports JPEG, PNG, GIF, BMP, TIFF and WebP.

This package provides a color-correct image viewer for the terminal. Your terminal should support the Kitty Graphics protocol. If it doesn't, it should support the Sixel protocol.

Quick Image Viewer is a small and fast GDK/Imlib2 image viewer. Features include zoom, maxpect, scale down, fullscreen, slideshow, delete, brightness/contrast/gamma correction, pan with keyboard and mouse, flip, rotate left/right, jump/forward/backward images, filename filter and use it to set X desktop background.

The hydrus network client is an application written for internet-fluent media nerds who have large image/swf/webm collections. It browses with tags instead of folders, a little like a booru on your desktop. Advanced users can share tags and files anonymously through custom servers that any user may run. Everything is free and privacy is the first concern.

xzgv is a fast image viewer that provides extensive keyboard support.

Catimg is a little program that prints images in the terminal. It supports JPEG, PNG and GIF formats.

qView is a Qt image viewer designed with visually minimalism and usability in mind. Its features include animated GIF controls, file history, rotation/mirroring, and multithreaded preloading.

qpageview provides a page based document viewer widget for Qt and PyQt. It has a flexible architecture potentionally supporting many formats. Currently, it supports SVG documents, images, and, using the Poppler-Qt5 binding, PDF documents.

Nomacs is a simple to use image lounge featuring semi-transparent widgets that display additional information such as metadata, thumbnails and histograms. It is able to browse images compressed archives and add notes to images.

Nomacs includes image manipulation methods for adjusting brightness, contrast, saturation, hue, gamma, and exposure. It has a pseudo color function which allows creating false color images. A unique feature of Nomacs is the synchronization of multiple instances.

feh is an X11 image viewer aimed mostly at console users. Unlike most other viewers, it does not have a fancy GUI, but simply displays images. It can also be used to set the desktop wallpaper. It is controlled via commandline arguments and configurable key/mouse actions.

Überzug++ is a command line utility written in C++ which allows to draw images on terminals by using X11/Wayland child windows, sixels, kitty and iterm2.

Advantages over w3mimgdisplay:

• Support for Wayland: Sway, Hyprland, niri and Wayfire

• No race conditions as a new window is created to display images

• Expose events will be processed, so images will be redrawn on switch workspaces

• Tmux support on X11, Sway and Hyprland

• Terminals without the WINDOWID environment variable are supported

• Chars are used as position - and size unit

• No memory leak (usage of smart pointers)

• A lot of image formats supported (through OpenCV and libvips).

• GIF and animated WEBP support on X11, Sixel, Sway and hyprland

• Fast image downscaling (through OpenCV and OpenCL)

• Cache resized images for faster viewing

ytfzf is a POSIX script that helps you find PeerTube or YouTube videos without requiring API and opens/downloads them using mpv/ytdl.

pqiv is a GTK-3 based command-line image viewer with a minimal UI. It is highly customizable, can be fully controlled from scripts, and has support for various file formats including PDF, Postscript, video files and archives.

This package provides a user-friendly terminal image viewer that uses graphic capabilities of terminals (Sixel, Kitty or iterm2), or 24-Bit color capabilities and unicode character blocks if these are not available.

nsxiv is a fork of sxiv. Its primary goal is to provide the most basic features required for fast image viewing. It has vi key bindings and works nicely with tiling window managers. Its code base should be kept small and clean to make it easy for you to dig into it and customize it for your needs.