Jp2a is a small utility that converts JPEG images to ASCII.

libjpeg-turbo is a JPEG image codec that accelerates baseline JPEG compression and decompression using SIMD instructions: MMX on x86, SSE2 on x86-64, NEON on ARM, and AltiVec on PowerPC processors. Even on other systems, its highly-optimized Huffman coding routines allow it to outperform libjpeg by a significant amount. libjpeg-turbo implements both the traditional libjpeg API and the less powerful but more straightforward TurboJPEG API, and provides a full-featured Java interface. It supports color space extensions that allow it to compress from and decompress to 32-bit and big-endian pixel buffers (RGBX, XBGR, etc.).

Converseen is an image batch conversion tool. You can resize and convert images in more than 100 different formats.

GGG (Guile Glyph Generator) is a command-line utility that allows you to generate pretty images/badges which can be used for your projects, announcing tech used, sponsoring and appreciating other projects, distinguishing versions of things supported, etc.

GGG is highly configurable, reads Scheme files where you define your tasks, and supports badges between one and three parts. It leverages SVG generation from Lisp and S-expressions, building pixel perfect badges.

SNG (Scriptable Network Graphics) is a minilanguage designed specifically to represent the entire contents of a PNG (Portable Network Graphics) file in an editable form. Thus, SNGs representing elaborate graphics images and ancillary chunk data can be readily generated or modified using only text tools.

SNG is implemented by a compiler/decompiler called sng that losslessly translates between SNG and PNG.

jpegoptim provides lossless optimization (based on optimizing the Huffman tables) and "lossy" optimization based on setting maximum quality factor.

Leptonica is a C library and set of command-line tools for efficient image processing and image analysis operations. It supports rasterop, affine transformations, binary and grayscale morphology, rank order, and convolution, seedfill and connected components, image transformations combining changes in scale and pixel depth, and pixelwise masking, blending, enhancement, and arithmetic ops.

Steghide is a program to `hide' data in various kinds of image and audio files. This practice is known as steganography, but the method used by steghide is not very secure and should not be used where security is at stake. Even if a password is used, steghide offers little plausible deniability.

Nonetheless, neither color nor sample frequencies are changed, making the embedding resistant against first-order statistical tests not aimed specifically at this tool.

Nifti_clib is a set of I/O libraries for reading and writing files in the nifti-1, nifti-2, and (to some degree) cifti file formats. These are binary file formats for storing medical image data, e.g. MRI and fMRI brain images.

grim can create screenshots from a Wayland compositor.

PerceptualDiff visually compares two images to determine whether they look alike. It uses a computational model of the human visual system to detect similarities. This allows it too see beyond irrelevant differences in file encoding, image quality, and other small variations.

WebP is a new image format that provides lossless and lossy compression for images. WebP lossless images are 26% smaller in size compared to PNGs. WebP lossy images are 25-34% smaller in size compared to JPEG images at equivalent SSIM index. WebP supports lossless transparency (also known as alpha channel) with just 22% additional bytes. Transparency is also supported with lossy compression and typically provides 3x smaller file sizes compared to PNG when lossy compression is acceptable for the red/green/blue color channels.

Phockup is a media sorting tool that uses creation date and time information in photos and videos to organize them into folders by year, month and day. All files which are not images or videos or those which do not have creation date information will be placed in a folder called unknown.

APNG (Animated Portable Network Graphics) is an unofficial extension of the APNG (Portable Network Graphics) format. APNG patch provides APNG support to libpng.

Collection of graphics images created to test PNG applications like viewers, converters and editors. As far as that is possible, all formats supported by the PNG standard are represented.

Libtiff provides support for the Tag Image File Format (TIFF), a format used for storing image data. Included are a library, libtiff, for reading and writing TIFF and a small collection of tools for doing simple manipulations of TIFF images.

Gifsicle is a command-line GIF image manipulation tool that:

• Provides a batch mode for changing GIFs in place.

• Prints detailed information about GIFs, including comments.

• Control over interlacing, comments, looping, transparency, etc.

• Creates well-behaved GIFs: removes redundant colors, only uses local color tables, etc.

• Shrinks colormaps and change images to use the Web-safe palette.

• Optimizes GIF animations, or unoptimizes them for easier editing.

Two other programs are included with Gifsicle: gifview is a lightweight animated-GIF viewer, and gifdiff compares two GIFs for identical visual appearance.

libspng is a simple C library for loading Portable Network Graphics (PNGs), intended as an easy-to-use replacement for libpng.

The JasPer Project is an initiative to provide a reference implementation of the codec specified in the JPEG-2000 Part-1 standard (i.e., ISO/IEC 15444-1).

libheif is an ISO/IEC 23008-12:2017 HEIF and AVIF (AV1 Image File Format) file format decoder and encoder.

libungif is the old GIF decompression library by the GIFLIB project.

Flameshot is a screenshot program. Features:

• Customizable appearance.

• Easy to use.

• In-app screenshot edition.

• DBus interface.

• Upload to Imgur.

Simple encoder and decoder for blurhashes. Contains a command line program as well as a shared library.

Developer's Image Library (DevIL) is a library to develop applications with support for many types of images. DevIL can load, save, convert, manipulate, filter and display a wide variety of image formats.