Hi Ralph, On 11/14/20 9:03 AM, Ralph Little wrote: > Hi, > I am hoping to garner some opinions about an issue that I am having with > testing a Canon imageClass machine with the pixma backend. > > I have an imageClass MF4770N machine that has always been a little > problematic on the ADF and I have never really understood why. > With Rolf we managed to get the machine fairly well supported but > sometimes the machine would fail with a service code and abort requiring > a power-cycle. > > I recently managed to track down the specific behaviour that caused this > issue but I am not sure how to deal with it. > > When scanning on the ADF, if the user selects a scan area that is > aligned to both the hard left and hard right of the scan area, then the > machine scans OK. However, if the selection is away from the left area, > the selection can not extend within 32 pixels of the right hand side. > Within that restriction, I can scan whatever I want. > > In order to scan a selection that aligns with the right hand side, the > select must align with the left hand side also. > > This, I think is a bug in the machine's firmware. I just checked and it > is fully up-to-date so it looks like there are no fixes coming. > > On Windows, when using the ADF, one can only select a fixed media type > that is centred in the scan area. One cannot arbitrarily select a scan > area. So it is not possible to see what the Windows driver would do > because the scenario is impossible. > > My problem is how to deal with the issue in the Pixma backend. The > common scan scenario in ADF is to scan Letter media which is a full > width scan. I cannot just make the maximum width 32 pixels less to avoid > the problem. In 75dpi, 32 pixels is a significant chunk to miss from the > right hand side. > > Any ideas?
Could it be that there's some alignment requirement? E.g. the scanner requires that the left hand side pixel offset is a multiple of 32, or maybe the pixel count must be a multiple of 32 or something like that? I've seen similar things on the genesys backend. Cheers, Povilas
