These Adobe Photoshop alternatives for Linux will help you edit images with ease.
If any program could be considered "the open-source version of Photoshop", it would be GIMP (GNU Image Manipulation Program). GIMP has been around since 1995 (Photoshop launched in 1988) making it one of the oldest open source applications available.
It's a flexible tool that includes several core features that replicate many of the same effects as Photoshop. GIMP is also built with extensibility in mind, meaning you can add new functionality by installing third-party plugins.
In short, GIMP is powerful enough to suffice in a professional capacity. The only downside is that GIMP specifically avoids copying Photoshop's interface. Although a strong Photoshop alternative, you'll have a bunch of new keystrokes and menu commands to learn.
To install GIMP on Linux, begin by adding a PPA repository, then update sources and install:
sudo add-apt-repository ppa:otto-kesselgulasch/gimp
sudo apt update
sudo apt install gimp
On Windows, one of the better alternatives to Photoshop is the free image editor, Paint.NET. An alternative to MS Paint, it's flexible and extensible through plugins, and more lightweight than Photoshop.
The Linux equivalent of Paint.NET is Pinta, an app that comes with everything you need right out of the box. This includes all the basic and core functions, unlimited layers, full edit history, and over 35 effects for image adjustments. You can also switch between a docked interface and a free-floating window interface.
While GIMP offers a substantial Photoshop-like experience, Pinta is ideal for quick image retouching and simple edits.
Pinta can be installed from default repositories, but this may be an old version. To guarantee you're installing the latest Pinta, grab it from the repository provided by Pinta's developers:
sudo add-apt-repository ppa:pinta-maintainers/pinta-stable
sudo apt update
sudo apt install pinta