# Options for storing and converting image data

Each image stored in a TIFF-F file has a specific set of image format characteristics. TIFF-S files always store the image using 1D encoding, low resolution, and A4 page width. During image transfer, the image characteristics of the stored image may be different from the values of the image being sent or received. Image format conversion can occur on-the-fly during the fax session, or it can be initiated offline by the application.

Consider these factors when you design your application, select your TIFF-F file storage characteristics, and determine your conversion settings:

Factor | Description
Machine restrictions | Not all fax terminals can handle the full range of image characteristics. A more capable machine always supports the values of a less capable machine. At the start of a fax session, the receiver announces its capabilities (DIS frame). The sender chooses the image format for the transmission (DCS frame) within the limits of the receiver's capabilities. If the file to be sent has an image format that is beyond the capabilities of the receiver, the sender must perform on-the-fly image conversion.
File size | Some image formats consume less data storage space than others, but may require more CPU resources from the host system for encoding. You may want to use a particular format for all transactions if data storage space and transmission time (and telephone charges) are primary considerations for application design.
CPU resources | Converting between one image format and another requires host processor execution time. The execution time required for conversions is the limiting factor if the system's CPU is heavily loaded by database or other operations in addition to fax functions. The application may accept a longer transmission time in return for conserving CPU resources. Offline conversion of an image from one format to another can be performed to help minimize the execution load.
Bad line replacement | NaturalFax performs bad line analysis by decoding a line and comparing its length in pixels to the line length appropriate to the page width in use. During image conversion, bad lines may be eliminated or replaced, as determined by the value of the badlineaction parameter.
Document compatibility | NaturalFax transmits files that are in TIFF-F or TIFF-S format. The TIFF-F files may have different image attributes on different pages. NaturalFax performs on-the-fly conversions to ensure that mixed image files are transmitted as a single document.