[sane-devel] Lexmark experimental backend

[Stéphane VOLTZ]

	Hello,

	I have just committed a new version of the experimental/lexmark backend. From 
the current regular backend it brings:

	- arbitrary scanarea selection
	- gain calibration
	- offset calibration
	- software shading calibration
	- Dell A920 support
	- infrastructure for adding more models

	I believe the experimental is in good shape to get into regular CVS. However, 
while I took care of not altering X1100 support, and since I don't have such 
a model to test, there may be bugs for this model. So it needs testing.
	For A920 1200 dpi scan is disabled, since it does 1200x600, and so needs 
to "inflate" lines to match 1200x1200. Which is a little tricky since the 
data copying expects even/odd columns interleaved.
	Last issue is shading calibration. This scanner has no hardware shading 
calibration, and it has to be done in software. The current correction 
implementation gives good results, but shows deficiency in dark areas. The 
trouble is due to the fact that correction depends of the sensor element that 
corresponds to the scanned column, but also slightly depends on his 
neighbours in a way I couldn't figure out. Someone more clever than me will 
have to find it.
	Pictures given "out of the box" are correct, and with little tweaking of 
gamma and light from the frontend, one can have good scans.

Regards,
	Stef