[sane-devel] xsane-0.87 released

Henning Meier-Geinitz henning@meier-geinitz.de
Wed, 17 Jul 2002 19:29:28 +0200


On Tue, Jul 16, 2002 at 08:25:06PM +0200, Rene Rebe wrote:
> Speaking about the preview feature of xsane ... - for color scans
> xsane does a scan with gamma=1 and creates a software preview when the
> user modifes the gamma value. But for my avision backend the scanned
> images are not as light as they are in the xsane preview. Although the
> scan looks reasonable for the gamma value.

Same here for the mustek_usb backend. The preview is slightly brighter.

> So is the software simulation much too light (because of the loss of
> precision) or are the Avision scanners interpreting the values in a
> different way I think, and so the scanned images are just too dark for
> the gamma-table I send?
The mustek_usb backend does the calculation in software. Maybe it's
wrong but I think it just uses the gamma vectors as array like this:

corrected_value = gamma_table [really_scanned_value]