Option Value Unit

Member unit specifies what the physical unit of the option value is. The possible values for type SANE_Unit are described in Table 4.4. Note that the specified unit is what the SANE backend expects. It is entirely up to a frontend as to how these units a presented to the user. For example, SANE expresses all lengths in millimeters. A frontend is generally expected to provide appropriate conversion routines so that a user can express quantities in a customary unit (e.g., inches or centimeters).

表 4.4: Physical Units (SANE_Unit)

Symbol	Code	Description
SANE_UNIT_NONE	0	Value is unit-less (e.g., page count).
SANE_UNIT_PIXEL	1	Value is in number of pixels.
SANE_UNIT_BIT	2	Value is in number of bits.
SANE_UNIT_MM	3	Value is in millimeters.
SANE_UNIT_DPI	4	Value is a resolution in dots/inch.
SANE_UNIT_PERCENT	5	Value is a percentage.
SANE_UNIT_MICROSECOND	6	Value is time in $\mu$-seconds.