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Subject: Re: Plustek 9636T scans color/grey incorrectly FURTHER
From: Mark Bratcher
Date: Tue, 23 Jan 2001 22:51:48 -0500

OK, I tried several tests. Here is my setup:

RedHat Linux 6.2
Kernel 2.4.0
Plustek Driver 0_37_23
Sane 1.0.3
XScanImage (resolution 200, color, normal)
"if 1" set in plustek_scan.h (the default setting)
Scan subject: a small envelop with black writing and colorful postage
stamp

First set of tests

0. Open XScanImage

1. Prescan: came out purple

2. Prescan: almost OK, but had some "jogged" scan lines, black has cyan
shadow

3. Prescan: same as #2

4. Prescan: same as #2 plus faint vertical purple stripes 

5. Prescan: same as #2

6. Scan: white areas came out cyan, and black had yellow-green shadows

7. Close XScanImage

Second set of tests

0. Open XScanImage

1. Scan: same as #2 in first test

2. Prescan: no obvious jogging, some vertical stripes in white
background

3. Prescan: No obvious jogging, a lot more vertical stripes in white
background

4. Prescan: same as #2 in first test

5. Scan: white areas OK, black has yellow shadow

6. Scan: white areas light green, black has yellow shadow

7. Scan: white areas purple, black has two different shadows

8. Close XScanImage

I did several more similar tests. I also did some with "if 0" set in
plustek_scan.h and recompiled/installed the plustek driver. If anything,
the "if 0" scans tended to come out worse (one was not only discolored,
but horribly skewed). But overall I never got a 100% good scan. I think
I'd have to run quite a few more tests (100? 1000?) to statistically
claim that "if 0" is really different than "if 1" in results.

Also, although I did not run many tests on kernel 2.2.17, I was seeing
the same type of failures there.

Mark

plustek@linuxhacker.org