LazPaint can open and save files in the most common image formats, including JPEG and PNG.
While it can open Paint.NET's layered .pdn files, which could be a boon for users who see it as a possible complementary package, it's unable to save files in the .pdn format. That means that this ability will be probably only be of real use to those who are choosing to change to LazPaint from Paint.NET, so that they will be able to continue using their legacy files with minimum trouble.
Help and Documentation
Under the Help menu, there is an option for Index, which takes you to a basic Wiki page with a bit of information about LazPaint. It's not the most comprehensive or well structured help resource that I've ever come across, though in fairness that is a complaint that can be leveled at a large number of open source projects.
During the course of this review, I've leveled some criticisms at features that I don't really understand and clicking the Help button in the app failed to lead me to any information that would clarify these issues.
For the record, I should note that there are some video tutorials available on YouTube, but that is hardly an ideal way to find information on how to use a specific tool or feature.
I had hoped that LazPaint would prove to be a real alternative to Paint.NET, as that is an image editor that suffers from a few compromises. However, despite its weaknesses, I believe Paint.NET still presents a more compelling case than LazPaint. I don't think that many established Paint.NET users would jump ship for LazPaint, though there are a few features that could tempt some to consider it as a complementary image editor.
For image editor newbies who aren't looking for an overly powerful package or to enhance their photos, I believe that it is worth taking a look at. I'm sure that there will be some new users who prefer the approach that LazPaint takes in comparison to Paint.NET. The only caveat, though, is that the lack of comprehensive documentation could prove to be a barrier to new users getting acclimatized with the app.
You can download your own free copy of LazPaint from their Sourceforge page.