Exiv2 is a C++ library and a command line utility to manage image metadata. It provides fast and easy read and write access to the Exif, IPTC and XMP metadata of images in various formats.

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

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

JPEG XR is an approved ISO/IEC International standard (its official designation is ISO/IEC 29199-2). This library is an implementation of that standard.

Gradia is a GTK 4 application for enhancing and preparing screenshots for blogs, social media, and documentation. It supports background customization, annotation tools (pen, arrow, text, highlight, stamp), padding, cropping, and various export formats.

grim can create screenshots from a Wayland compositor.

Zimg implements the commonly required image processing basics of scaling, colorspace conversion, and depth conversion. A simple API enables conversion between any supported formats to operate with minimal knowledge from the programmer.

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.

VIGRA stands for Vision with Generic Algorithms. It is an image processing and analysis library that puts its main emphasis on customizable algorithms and data structures. It is particularly strong for multi-dimensional image processing.

Flameshot is a screenshot program. Features:

• Customizable appearance.

• Easy to use.

• In-app screenshot edition.

• DBus interface.

• Upload to Imgur.

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.

Libjpeg implements JPEG image encoding, decoding, and transcoding. JPEG is a standardized compression method for full-color and gray-scale images. It also includes programs that provide conversion between the JPEG format and image files in PBMPLUS PPM/PGM, GIF, BMP, and Targa file formats, as well as lossless JPEG manipulations such as rotation, scaling or cropping:

1. cjpeg

2. djpeg

3. jpegtran

4. rdjpgcom

5. wrjpgcom

pngcheck verifies the integrity of PNG, JNG and MNG files (by checking the internal 32-bit CRCs, a.k.a. checksums, and decompressing the image data); it can optionally dump almost all of the chunk-level information in the image in human-readable form. For example, it can be used to print the basic statistics about an image (dimensions, bit depth, etc.); to list the color and transparency info in its palette (assuming it has one); or to extract the embedded text annotations. This is a command-line program with batch capabilities (e.g. pngcheck *.png.)

Also includes pngsplit which can split a PNG, MNG or JNG file into individual, numbered chunks, and png-fix-IDAT-windowsize that allows resetting first IDAT's zlib window-size bytes and fix up CRC to match.

Libavif is a C implementation of AVIF. It can encode and decode all YUV formats and bit depths supported by AOM, including with alpha.

pngquant is a PNG compressor that significantly reduces file sizes by converting images to a more efficient 8-bit PNG format with alpha channel (often 60-80% smaller than 24/32-bit PNG files). Compressed images are fully standards-compliant and are supported by all web browsers and operating systems.

Features:

1. High-quality palette generation using a combination of vector quantization algorithms.

2. Unique adaptive dithering algorithm that adds less noise to images than the standard Floyd-Steinberg.

3. Easy to integrate with shell scripts, GUIs and server-side software.

4. Fast mode for real-time processing/large numbers of images.

libyuv is an open source project that includes YUV scaling and conversion functionality. It can:

• Scale YUV to prepare content for compression, with point, bilinear or box filter.

• Convert to YUV from webcam formats for compression.

• Convert to RGB formats for rendering/effects.

• Rotate by 90/180/270 degrees to adjust for mobile devices in portrait mode.

Libiptcdata is a C library for manipulating the International Press Telecommunications Council (IPTC) metadata stored within multimedia files such as images. This metadata can include captions and keywords, often used by popular photo management applications. The library provides routines for parsing, viewing, modifying, and saving this metadata.

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

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

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.

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.

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

OptiPNG is a PNG optimizer that recompresses image files to a smaller size, without losing any information. This program also converts external formats (BMP, GIF, PNM and TIFF) to optimized PNG, and performs PNG integrity checks and corrections.