OmniPage, HP scanners and TWAIN drivers: a follow-up

Last time, we posted an item from Caere stating that problems using OmniPage with HP scanners were, in part, attributable to the fact that there were no HP TWAIN drivers. Several readers disputed this assertion.

Caere's David Ramsey, the author of the original message from Caere, offered this reply:

Mea culpa for saying that HP doesn't have any TWAIN drivers for the Mac. Obviously DeskScan is in fact a TWAIN driver. However, that doesn't really change the situation, 'cause you still can't scan directly from OmniPage. Here's why:

Pro 8 supports two scanning protocols: Pixel Translations' "Isis" drivers and TWAIN sources. Which driver is used for a given scanner depends on the scanner's entry in the "Caere Scanner Catalog" file, located in System Folder->Extensions->Caere Libraries. If you open this file (It's just a SimpleText file) and scroll down to the HP section, you'll see that all the HP scanners are controlled via Pixel drivers.

When OmniPage owners started moving to 8.5 and 8.5.1, we received a flood of reports of scanners not working, which we were able to easily duplicate here. The problem seemed to be the Pixel drivers - simply clicking on the driver in the Chooser (although Pro 8 doesn't use the Chooser as a selection mechanism, selecting a driver in the Chooser initializes it and is useful as quick test) would freeze or crash the system. Dropping back to < 8.5 cured the problem.

This didn't happen with all Pixel drivers - Epson drivers, for example, seem to work - but it did happen with HP and Nikon drivers.

We added TWAIN support in Pro 8 to address the problems with Pixel drivers. Unfortunately, many manufacturers supply TWAIN sources that (when used through the "private" interface Pro uses, as opposed to the "public" "Acquire..." type interface), are, shall we say, problematic. Pro has to query the scanner through the TWAIN source to get its capabilities-- scanner bed size, resolution, color format, and so forth. Although DeskScan was available when Pro 8 shipped, we didn't support it, relying instead on the existing Pixel drivers. Why? Basically, there are too many problems with this driver to make it usable for Pro.

The only problem here is that around a dozen readers have since written to say that they are in fact successfully using OmniPage Pro with DeskScan drivers. I asked David if he had some explanation that would reconcile this disparity, He added:

There were some versions of OmniPage LE - the "lite"variant shipped with many scanners - that had vendor-specific hacks. The Agfa version is a good example. I wasn't involved with any of these and it's entirely possible that some version of OmniPage LE works fine with a scanner that Pro 8 does not.

Beyond that, David had no explanation. However, he is currently investigating the MacFixIt reports and I hope to report further information soon.