For developing a web based scan solution, I would love to test it on Windows or Mac without actually hooking up a scanner to my box. So is there a program/tool that emulates or gives me a virtual twain source with some default image data?
The Twain sample driver that comes along with the twain sample application up on source forge should have what you're looking for.
http://sourceforge.net/projects/twain-samples/files/TWAIN%202%20Sample%20Application/
Yes, there are plenty of solutions for this. We are using TerminalWorks' UniTwain application. The users are very satisfied as it is pretty simple to use and it does it's job. This is the download link: http://www.terminalworks.com/unitwain
both of above are paid apps. there is one open source: http://sourceforge.net/projects/twain-samples/files/
you need Data Source, it adds virtual scanner, which gives you the file if asked. dont know if the received sample file can be changed, but for testing its good.
来源：https://stackoverflow.com/questions/5381677/simulate-or-virtual-twain-source-for-twain-development