There is only one file type that uses the .KDI extension:
KD Player Skin Image File
Image file used by KD Player, a free Java ME (Micro Edition) audio player for mobile devices; stores the graphics for the skin in a .JPG, .PNG, or another standard bitmap format; used for styling the music player's buttons, background, and other elements.
Like many other skin formats, KDI files are saved with a layout settings (.KDS) file in a .ZIP archive, which is the skin for the player. The KDS file maps the graphics in the KDI graphic to the user interface elements.
NOTE: KDI files can be opened by any image viewer. For convenience, you can rename the ".kdi" extension to ".jpg" or ".png" while editing the graphics, and then change it back to ".kdi" when packaging the skin.
Updated: May 22, 2011