The default value is 25.

Valid values are 0 to 255.

Note: This value sets the allowable amount of change in the background color across an image. An example of this would be a book page scanned on a flatbed scanner, where one edge was darker than the rest due to the greater distances from the scanner bed. This image would have a relatively high background variance. The algorithm will suggest the adaptive correction method for images that exceed the allowable background variance.

BrightnessContrastOptions Object