Great option to other image editors and image creating software. It has a simple and intuitive user interface, yet supports both layers and 3D objects. Functional across all major OS. It is free, as in open source. It imports .PDN files created with Paint.NET without issues.
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...
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BatchPhoto - BatchPhoto is a batch photo editing software for Win and Mac that can convert, resize, annotate and watermark hundreds of photos in one go. Learn more and try it for Free!
Microsoft Paint - Paint (formerly Paintbrush) is a simple, ultra-basic graphics painting program that is included...
Batch Image Converter - Convert multiple images, photos, and pictures between 30+ formats: JPG, PNG, GIF, TIFF, BMP, JP2, J2K, TGA, PSD, RAW, DDS, PNM, WMF, ICO, SGI, HDR, LBM