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GIMP isn't the first thing people will think of when you say Pixel Editor, but if you set it up nicely you can get some really cool things working for you in it. As you can see in the cover image, you can set it up to work very nicely for pixel art with the preview panels in different zoom values that update as you place each pixel, this helps a lot with static pixel art and sprite concepts in general!
SpecsUpdate
Pros
Pro Free, open source and cross-platform
GIMP is completely free and open source, meaning you can use GIMP and all of its features without spending a penny. This makes it an excellent choice for artists or designers who may not have the budget to spend over 700 USD on Photoshop. It is also available for free on Windows, Mac OS, and Linux. It's licensed under GPL with source code available here.
Pro Active and helpful community
GIMP has an active community that makes it easy to find help when needed. Many users have created third party tutorials, so it's easy to discover information on how to do different things with GIMP. Check here for links to the different GIMP communities and tutorials.
Pro Beginner-friendly
Gimp has less features than programs like Photoshop. In that case, if you are a beginner, or someone who doesn't require complicated options, Gimp is the perfect choice. It allows you to quickly perform basic photo manipulation so you can easily get the product you need without having to worry about complicated features getting in the way.
Cons
Con User interface is terrible
Many simple tasks are complicated in GIMP. For example, changing the brush size is annoying. Basically the UI is not bad, but not very good either.
Con Lacks adjustment layers
Adjustment layers offer a non-destructive way of combining different photo manipulations. Without adjustment layers, the only way to see changes is by irreversibly editing the image.
However, they are promised to come with future updates.
Con GIMP graphics acceleration is pretty bad
GIMP originally was completely raster but as video graphic cards became bigger and better and more useful and as more apps started having UI/canvas graphic acceleration options there was a desire for GIMP to do the same. But GEGL is mainly used for certain filters and effects and not the whole application canvas or UI and is quite broken and incomplete not on par with what even say Krita has. As it stands fully accelerated GIMP will probably come about in 10 years from now. By that time the whole suit might be completely useless.
Con Incredibly slow development cycle
It can take 2-5 years for a new version to be released. To make matter worse GIMP development is winding down. The interest in developing this software has seen a decline over the years from the highest peak around 2010-2014. Right now there are only a handful core devs left.
Recommendations
Comments
Flagged Pros + Cons
Con Less features than other programs
Being a free program, it shouldn't be surprising that it has limited features. For those needing more advanced features for something more professional, GIMP just isn't for you.