...
*Images with embedded alphas can use the alpha as a layer mask
It can be useful to convert a simple low dynamic range bitmap into a MXI which can then be used as an emitting texture in your scenes (only images in Mxi, Exr or Hdr formats can be used as emitting textures). To do this, after loading the image you can use the Intensity settings from the Edit panel (MXI section) to change the brightness of the MXI emitter. Brighter settings will make the MXI emit more light. Use the “Save MXI as” menu option to save the image in the MXI format. Please note that if your bitmaps are in HDR or EXR format they do not need to be converted to the MXI format; you can use these formats directly as Image Emitters. And keep in mind that by simply changing your image format to a high dynamic range format (Mxi, Exr or HDR) won't make its dynamic range to be higher (the information is the same you previously had), only the file format has change, but it allows you to use that image in certain uses (like emitting textures or Image Based Lighting).