--overscanmode

--overscanmode value

Sets the overscan value of the page when acquiring images. The device must support setting the overscan of pages. Some devices do not support setting the overscan.

The Overscan is used to scan outside of the boundaries described by the page (or acquisition area frame, see --area), and is used to help acquire image data that may be lost because of skewing.

For example, overscan can be visually described by the illustration below:

clip0037

The frame is the acquisition area that is defined. If overscan is supported, then the device is capable of scanning in the inter-document gap to get the skewed image information.

The valid options for the overscan value are as follows:

value	Definition
none	No overscan is used
auto	The device detects which part of the page is outside the boundaries of the page.
topbottom	Detect overscan only on the top and bottom of the acquisition area
leftright	Detect overscan only on the left and right of the acquisition area.
all	Detect overscan on all sides of the acquisition area.

See also the --deskew option for automatic deskewing. In many cases, it may be required to allow overscan to be used when automatic deskewing is enabled for situations where not only the page may be disoriented, but so much so that some of the page lies outside of the acquisition frame.

Example:

Acquire to a bmp file called test.bmp, and allow the device to use overscan to retrieve any part of the page that may lie outside of the acquisition area:

twainsave --filename test.bmp --overscanmode all

Default Setting:

The overscanmode value is set to none