A command conversion interface between an image machine with a plurality of hard keys and an image requestor is disclosed. When the command conversion interface detects and determines the activation of a specific hard key of the image machine, digital image information from the image machine is provided for the image requestor through the command conversion interface to execute a designated task, which has not been built in the image machine. In the command conversion interface, the designated task is interpreted by a destination command script, and the destination command script is processed by a compiler along with the digital image information, then transmitted to the image requestor to execute the task. The relationship between the specific hard key and the designated task refers to a new correlation table of the command conversion interface.