1 Aug 2004 15:39
Re: reverse engineering techniques
Henning Meier-Geinitz <henning <at> meier-geinitz.de>
2004-08-01 13:39:33 GMT
2004-08-01 13:39:33 GMT
Hi, On Wed, Jul 21, 2004 at 06:26:26PM -0400, Dave Burns wrote: > Let me try an example which someone out there might solve readily for all I > know. I can see the parameters where other drivers control the RGB gain and > gamma curves (at least I think they specify gamma curves). Gain is usually one value that inluences the whole image. At least for the scanners I know it's used the set the amplification of the analog frontend (AFE) during calibration. Hardware gamma curves are nor supported by every scanner. > RGB gain is fine, > I have the values for that figured out. But there are two other values per > RGB channel that remain unknown to me. The first value ranges from 0-63 and > may have something to do with a black point (but not sure of that). Maybe offset? Think of gain as the amplification and offset as the zero point. > Typical > values across RGB are 47, 36, 36. The second value is made up of two bytes. > I'm not 100% sure though that it is a short int. Since the 1st byte is only > ever a 1 or 0 and when I've graphed scanned image data with varying values, > there's a big discontinuity in the data. Typical values that give good > results for me are 0x119, 0x108, 0x106. But I've also see weird combinations > like 0x115, 0x9, 0x5. These combinations were from a driver that does > autoexposure. If it helps, I can tell what the sequence is that the driver > goes through before settling on those values (it iterates from a known(Continue reading)
should get write access to the repository to do the necessary
changes on your own...
Ciao,
Gerhard
On Tuesday 03 August 2004 08:35, Ullrich Sigwanz wrote:
> Hello Henning, Hello Gerhard
>
> I (developer of in the niash project - ullsig ) tested Gerhard's changes in
> source code.
> I substituted "our" files by Gerhard's files. Our testtool as well as a
> freshly patched sane tree compiled and worked fine.
>
> The changes can be approved.
>
> Here is a short status summary of the project:
>
> All 4 supported Scanners ( HP ScanJet 3300C, 3400C, 4300C and Agfa SnapScan
> Touch ) now work reasonably well as forum posts show
> Only color scans are supported
> The only transfer method is via "libusb". libieee1284-support and
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