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Why is setting PixelType not working when negotiating Twain Session?
原标题:

I m trying to specify programmatically settings for scanning in TWAIN session. Because amount of code here would be significant I m going to try to explain the problem without pasting the entire code. I hope there s someone good at TWAIN to help me....

To do scanning settings I m using lowlevel calls to native Twain library. The scanner is HP Scanjet 7000. At the moment I m stuck with setting colour and bit depth options. What is important I haven t had any problems with two other scanners. just this model.

According to the specification before setting ICAP_BITDEPTH (page 480) I need to set ICAP_PIXELTYPE (535). So first I m asking for the list of supported PixelTypes... And they are TWPT_BW (Black&White), TWPT_GRAY (Gray) and TWPT_RGB (RGB). Since I want to get black&white scans I m trying to set this capabilityt to TWPT_BW. This results in an error and I don t understand why. As I said in two other models this is working.

Is it possible that this scanner disallows setting capabilities like this?

TWAIN Specification: http://www.twain.org/docs/TWAIN_2_1_Spec.pdf

最佳回答

This problem turned out to be a specification issue. It appears that hp scanjet scanners when setting PixelType they require TwainType.UInt16 and I was setting TwainType.Int16 as the first parameter. Thank you to user AlexKak I found the answer to this problem. http://www.codeproject.com/KB/dotnet/twaindotnet.aspx?msg=1313293#xx1313293xx

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