Problem with TwainTransferMechanism.Memory and auto detectio

[remy]

Hy,

When I scan an A4 Page using TwainTransferMechanism.Memory, half of the result image is black. It looks like the page format is not detected whereas auto detection is activated.
With TwainTransferMechanism.native or if I scan a page with settings A4 landscape and TwainTransferMechanism.Memory, I don’t have problem

Thanks for your help

[Robby Jackson]

Hi Remy,

Does your computer has sufficient memory to hold the scanned images? If this is not the case, it would be helpful to paste your source code here.

With TwainTransferMechanism.native or if I scan a page with settings A4 landscape and TwainTransferMechanism.Memory, I don’t have problem

When you try these two options, did you change the other properties, such as the resolution?

In addition, did you have the same problem with Twack?

[remy]

Hi Robby,

I don’t think that my computer memory is a problem, I have 4 Go.
During my tests, I changed only page format (auto, A4landscape) and TwainTransferMechanism.Memory or TwainTransferMechanism.Native.
With TwainTransferMechanism.Native, I am no problem.
With TwainTransferMechanism.Memory, I am a problem only scan with auto detection.

I used twack and I tried to change TwainTransferMechanism.Memory or TwainTransferMechanism.Native, and I have always half of the result image black.

[spike]

This sounds like a possible driver bug…

What scanner are you using and (if you can find it) what version of the TWAIN driver?

Have you tested with any other scanner, particularly another brand or vendor?

[remy]

Hi spike,

I use a Canon DR6030C and the version of the driver TWAIN driver is 1.0.11 and version of firmware is 4.16.
I think that I have the last version.
I try only on the Canon scanners.

[spike]

Hmmm. Canon TWAIN drivers are, in general, very good. But I have seen some funny differences between Native transfer mode and Memory transfer mode, when the driver is doing some kind of smart processing.

Could you explain more what you mean by “auto detection”? What is that exactly?
Which half of the image is black?
is it *exactly* half?
Is it *exactly* black? (for example, you examine the pixel values and they are 0’s)
The other half looks exactly right?
Any chance you could attach an example to your reply, as a TIFF file?

Just to mention some things related to Robby’s question: it does not matter (for this) how much memory you have installed in the computer, because Windows uses virtual memory. Each 32-bit program is given 4GB of virtual memory to run in. Normally Windows takes up 2GB, leaving 2GB for your program and its data. If you scan an A4 page in color at 3000 DPI, the incoming image would require 2,610,260,100 bytes and your program will not be able to allocate that. This will happen on a machine with 2GB of RAM or a machine with 16GB of RAM, because the issue is related to the 32-bit virtual address space.

[remy]

The mode detect auto is a format of scan like A4 landscape or A4 portrait.
I’m sure that the half page is black (#000000) and the other half is very good.
I attached my page for that you see.

[spike]

Hi Remy – thanks for the TIFF files, now I understand. It would have been clearer if you had said that you are feeding A4 paper (I guess in landscape?) and the scanner is returning a 17″ x 12″ image with your paper on the right and black filled on the left.
You are correct that it is ‘half black’ but that leaves out a lot of important information.

This looks like a driver bug. I think your choices are (a) talk to Canon technical support or (b) work around the problem in your application.

If you are feeding the paper in portrait, have you tried feeding on the other edge of the feeder, or feeding landscape?
These are just work-around ideas. If you are feeding your paper landscape already, then this is definitely a driver bug.

[remy]

Hi Spike,
Yes, I works around the problem, I select transfert native for “detect auto” and transfert memory for “A4,A3,A5”.
Thanks for your help.

[Author]

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