On MacOS Pinta v1.4, I can launch Pinta and File->Open my image files. However, Pinta does not publish that it handles image file types, so it does not appear in "Open With>" for images. Also, if you manually choose Pinta to open an image file, Pinta provides an error "The doument XYZ.png could not be opened. mono cannot open files in the Portable Network graphics image format"...