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Paint.NET is a raster graphics editor, similar to Adobe Photoshop and GIMP, exclusively for the Windows operating system (Windows XP SP3 and up). Paint.NET is free, although its license is proprietary, and was originally designed as a powerful new alternative for Microsoft’s built-in Paint application on Windows. Over time, as it evolved, it grew to have additional features that rivaled even its competitors, including full support for a variety of plugins, layers, blending, and transparencies that modern raster graphics editors have standard support for. Because Paint.NET was specifically created for the Windows platform, it offers no support for other operating systems, but reverse-engineering its open-source roots made a third-party Paint.NET clone available for the mono and GTK platforms.
Originally conceived as a student project, Paint.NET was released in 2004 and has since evolved to a powerful image editor suite; although originally an open-source software, it was subsequently filed under Creative Commons license barring modification of the code, and then later to closed-source. Paint.NET is programmed using the C# language and uses the .pdn file format as its native one, which is a compressed representative of the object information of the project (which contains layers and layer information and so on).