[sane-devel] genesys backend

[Pierre Willenbrock]

Hi

The canon lide 35 is now scanning in color at any resolution. No
calibration yet. I'd like the calibration code to use a more generic
interface to the scanning logic before. But that will have to wait.

This time i want to propose a new mechanism for generating slope tables
in the genesys backend, which i implemented for my work.
In my opinion it is sufficient to describe one slope for each step type.
This slope is truncated as soon as the exposure time is reached. This
leads to a variable step count, which can be used to shorten the
acceleration/deceleration considerably.

I used slopes derived from a start step time(vstart), a final step
time(vend), a power(g) and a step count(steps):
p[i] = (i/(steps-1))^g
t[i] = vstart*(1-p[i])+vend*p[i]
For i in 0..(steps-1).

Pros:
+ less Constants
+ a means for calculating exposure time(which is limited by maximum
motor speed and number of pixels processed per line)
Cons:
- variable step count
- may be not applicable to all supported scanners
- breaks the current code

I attached the code i am using.

Related to this and just out of interest: Does the gl646 expect its
slope tables to contain STEPNO*2 resp. FASTNO*2 steps, too?

Regards,
  Pierre
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