Understanding TYMED
TYMED specifies the type of data transfer. The value of this member is derived from the WIA_IPA_TYMED common item property. The data transfer specified can be either a memory-callback transfer or a file transfer. See the Microsoft Windows SDK documentation for more information about the TYMED_XXX constants.
File Transfer TYMED
In a file transfer, the following values are used:
TYMED_FILE
Indicates one file containing a single image.
TYMED_MULTIPAGE_FILE
Indicates one file containing multiple images, such as multipage TIF and similar formats. This is used primarily in document feeder acquisition.
Memory Transfer TYMED
In a memory transfer, the following values are used:
TYMED_CALLBACK
Indicates one buffer containing a single image or multiple images separated by IT_MSG_NEW_PAGE messages.
TYMED_MULTIPAGE_CALLBACK
Indicates one buffer containing multiple images separated by IT_MSG_NEW_PAGE messages. This results in a single file containing multiple images. This is used primarily in document feeder acquisition.