Open Source C# Graphic Design Software for Mac

gPhoto is a program and library framework that lets users download pictures from their digital cameras. The libgphoto2 library gives you access to hundreds of models of digital cameras on several platforms. GIT repo and Issue tracker lives at https://github.com/gphoto/ these days.

FreeImage is a library project for developers who would like to support popular graphics image formats (PNG, JPEG, TIFF, BMP and others). Some highlights are: extremely simple in use, not limited to the local PC (unique FreeImageIO) and Plugin driven!

Developer's Image Library (DevIL) is a cross-platform image library utilizing a simple syntax to load, save, convert, manipulate, filter and display a variety of images with ease.

ImageMagick® is a free and open-source software suite for displaying, converting, and editing raster image and vector image files. It can read and write over 200 image file formats, and can support a wide range of image manipulation operations, such as resizing, cropping, and color correction. ImageMagick is written in C and is available for a wide range of operating systems, including Linux, macOS, and Windows. It can be used as a standalone application, or as a library that can be integrated into other software programs. Overall, ImageMagick is a powerful and versatile software suite for displaying, converting, and editing image files. Its support for scripting and automation, along with its other features, make it a valuable tool for a wide range of image-related tasks.

ImageStone is a powerful C++ class library for image manipulation. Its features include load, save, display, transformation, and nearly 100 special image effects. It can be used cross platform (includes Windows, Linux, Mac), and especially under windows it can be used as a DIB wrapper class.