JPEG 2000 supports the use of an alpha band or "alpha channel" for masking out portions of an image. GeoExpress supports creating alpha bands in JPEG 2000 files where the TIFF or JPEG 2000 source image has an alpha band.
When an image that has an alpha band is encoded to the JPEG 2000 format, GeoExpress encodes the alpha band losslessly to preserve its integrity.
NOTE: For users of GeoExpress Standard Edition, the encoding of the alpha band does not additionally decrement your data cartridge. Your encode job will be metered the same with or without alpha bands.