I make screenshots by copying the framebuffer with dd. IrfanView can read them as a RAW image, then save them as anything. Or you could append them to an appropriate flat ascii PGM header. For the K3 though, they are not perfect, but dpavlin
provided a tool in one of his posts to convert K3 framebuffer images to a standard format (but it still needs indexing if somebody finds it).
EDIT: Found and added to Tools index (framebuffer decoder for DX/DXG/K3):