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.
PhotoPenguin App - PhotoPenguin is a completely free batch photo editor with support for cropping, resizing, adding watermarks, and converting photos to other formats. It works on the user's device, using the capabilities of modern browsers.
GIMP - GIMP is a multiplatform photo manipulation tool.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
Microsoft Paint - Paint (formerly Paintbrush) is a simple, ultra-basic graphics painting program that is included...
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats