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.

GIFLIB is a library for reading and writing GIF images. It is API and ABI compatible with libungif which was in wide use while the LZW compression algorithm was patented. Tools are also included to convert, manipulate, compose, and analyze GIF images.

sjpeg is a simple encoding library for encoding baseline JPEG files. It is also a command-line tool that takes PNG or JPEG images as input to produce JPEG files.

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, OCR and various export formats.

Pngcrush optimizes PNG images. It can further losslessly compress them by as much as 40%.

Libpng is the official PNG (Portable Network Graphics) reference library. It supports almost all PNG features and is extensible.

Giblib is a simple library which wraps imlib2's context API, avoiding all the context_get/set calls, adds fontstyles to the truetype renderer and supplies a generic doubly-linked list and some string functions.

Gpick is an advanced color picker and palette editing tool.

Mtpaint is a graphic editing program which uses the GTK+ toolkit. It can create and edit indexed palette or 24bit RGB images, offers basic painting and palette manipulation tools. It also handles JPEG, JPEG2000, GIF, TIFF, WEBP, BMP, PNG, XPM formats.

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.

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.).

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.

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.

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

MyPaint is a simple drawing and painting program that works well with Wacom-style graphics tablets.

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

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.

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.

Libmng is the MNG (Multiple-image Network Graphics) reference library.

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.

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.

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.

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

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.