To all those eagerly waiting the CanoScan 3200F backend: a status update. During the past two weeks I have had less than ten hours for this, total. Despite that, I managed to hack together the unstaggering algorithm and now it is possible to get real looking scans in color and at 1200 dpi, too.
After Gerhard Jaeger's suggetion, I created account to Alioth and Henning Meier-Geinitz gave me developer access to the SANE CVS area. So, using those privileges I added the cs3200f backend codes, as they currently stand, to the experimental branch of the SANE. Feel free to take a look. Again, severe WARNING has to be kept in mind! The codes are experimental and in many cases there may appear anomalies which in the worst case may break the scanner, mechanically or electrically, so be careful and DON'T PLAY WITH THE CODES unless you want to take the risk or know what you are doing. At present the functionality is very limited. It is possible to make uncalibrated reflective scans in 8-bit gray and color. That basically works at all resolutions but I found out that at 75 dpi the scanner really does internally 100 dpi scans and decimates the results to 75 dpi, and in the case of color that is even more complex so that another decimation needs to be made in the driver. Now, I haven't yet figured out the exact way to compute the line count parameter for these cases, so the parameters in the code are more or less guesses. They may work but also may not and backend may hang at that resolution. I have not yet had time to figure out the proper way to make the motor speed ramps for the scans. The current ramp computation is based on parabolic speed curve and is not very good. Some kind of S-curve matched at both ends and limited to some reliably determined maximum acceleration is what is needed. Currently the exposure and speed is based on 12 Mbps USB so scanning is slow. Meaning, it could be much faster in 480 Mbps USB systems. Eventually I plan to support automatic speed detection but at present it is fixed. Now, even though the speed is slow, you may still sometimes see back-tracking. Unfortunately the speed curve used for back-tracking is not good enough and you may see artifacts due to that in the image. Currently there is no calibration for the geometry so it is likely that you will see something inside the scanner, too, besides what you have on the glass. That will be corrected when the calibrations are added. Those will also solve the uneven illumination (a feature of CCF-lamp) and streaks (a feature of CCD). Also due to lack of geometry calibration, it is possible to run the scan head to either end of the scanner. That causes worrying noise and I do not know if the mechanics has been designed to handle those collisions. I have not yet broken my HW but you might have worse luck, so don't do it. One way to do that is to use xsane preview, so don't use it. So, that's it, folks. I will continue on this even though slowly and post again when I have more news. With best regards, Lauri Pirttiaho Oulu Finland ................................................................... Luukku Plus paketilla p??set eroon tila- ja turvallisuusongelmista. Hanki Luukku Plus ja helpotat el?m??si. http://www.mtv3.fi/luukku
