Le Dimanche 28 Mai 2006 20:20, Fred Odendaal a ?crit?: > Stef, > > You are correct about the dot. I've attached 2 files: > find_start_lexmark1.pnm - This was with SANE_DEBUG_SANEI_USB=255 > find_start_lexmark2.pnm - This was with SANE_DEBUG_SANEI_USB unset. > > As you can see the picture gets better with usb logging turned off. I > think the real problem function is > sanei_lexmark_x1100_search_home_bwd(). It should have stopped the scan > head and positioned it inside the dot. The white space at the top of > each file is the distance past the dot that the scan head moved in the > reverse direction. In this function after the scan is stopped from > moving in the backward direction it is moved forward half the distance > of the dot plus the maximum no. of lines the buffer will hold. This is > done by the call to sanei_lexmark_x1100_move_fwd(). When I comment this > line out the picture gets even better. In other words, this function > isn't moving forward, but continuing backwards making our position even > worse! > > The sanei_lexmark_x1100_find_start_line() function is working as it > should. It simply scans what should be enough lines to scan past the dot > into white space and return the number of white lines past the dot. > Since the distance to the scanning area from the dot is known we simply > subtract how far past the dot we've moved from this number to see how > far we still have to go. > > regards, > Fred O.
Hello, you wre right, the trouble was with sanei_lexmark_x1100_search_home_bwd() which was scanning too far. To correct it, I made it read only one line of data (2500 bytes) at a time. So when it finds the dot and then stop, it is right on it. So we don't need to move forward a little. Now origin finding is slower but much more reliable. This change uncovered a bug in the way I modified rewind. So I had to change it. It now goes back by the bottom right y coordinate plus a fixed amount which is the distance between start of visible area and the "origin dot". I tweaked a little the calibration values. Picture are now close to the quality of my other scanner. I think that the current version is in good shape. Regards, Stef -------------------------------------------------------