Wikipedia
LazPaint
LazPaint is a raster image editor with layers. It aims at being simpler than GIMP. Rendering is done with antialiasing and gamma correction. It can read/write usual image formats and interoperate with other layered editors via OpenRaster format. It also imports Paint.NET files (with their layer structure) and Photoshop files (as flattened images). Also, it can import 3d objects in Wavefront (.obj) format.
It provides many color manipulation functions. Since version 6, there is a curve adjustments functions or RGBA channels and with HSL colorspace. There are complex selection functions, various filters and rendering of textures.