Interesting problem. - Long ago, I did this by using an OCR software that we bought to our company.
I have searched for an "updated" free OCR software, but have not found something easily to install and use. (have also looked at some "cheap" OCR software but not had time to evaluate them yet). It's not an easy problem. Imagine that the copies in "poor countries" is not as sharp and good as in other countries. Have they always access to these "special pens" that you write about? (what happen if they don't have it)? and choosing a specific type of pen did the (indian ink / color / red) to get the contrast is probably not easy either. I ponder if it's possible to make the holes in the paper with a pen/knife or something to get the contrast. Whichever method you use, it is a probably a requirement that the alternatives or the questions are not so close together. I also believe that the preprinted dark stripe or two would be good for alignment? A program language I would look on is "AutoHotkey" and the "pixelsearch" - But I have only use this command on screen. (and I can't use "ImageMaker" as good as I want). There was not much help, but anyway :-) Good luck! //Jan Glenn Linderman skrev: > Someone posed the question to me, if they could use their scanner for > grading multiple choice tests. This is for someone in a volunteer > teaching position in one of the less advanced, poor countries, but they > do have an image scanner available. So I'm not a real expert in > graphics manipulation and analysis, most of what I do in the way of > graphics is generating print images for books, so I mostly use > ImageMagick to help with some of the manipulations, but they are > simple... crops, resizings, adding margins, and the like. > > In thinking about the problem I see several steps, and several possibly > applicable uses of ImageMagick. > > Scan the answer sheet, which would be a bunch of pencil filled dots. > The locations of the dots would be known. Perhaps a preprinted dark > stripe or two would be good for alignment? Or even a surrounding box? > Is there a way to detect, and then rotate and translate known objects to > a fixed position, to compensate for misalignment of the papers in the > scanner? This seems to be the hardest thing, maybe because it is the > part I know least about. > > The scan could be done in color or greyscale, and then thresholded to > eliminate erasures... the use of soft, very black pencils is the norm in > those testing environments. > > Then, knowing where the answer dots would be, one would check for the > overall darkness of the enclosing region, and if it exceeds some > threshold it is considered marked. > > Once the set of marked boxes is known, the actual scoring, or grading, > is straightforward logic. The test creator would simply supply a list > of "correct answer" boxes, possibly a weighting for certain "partially > correct answer" boxes, and others would be assumed "incorrect answer" > boxes. Some rules about whether or not multiple boxes are allowed or > required to be a "correct answer". Multiple choice doesn't only mean > one choice, always. So the grading rules might be complex, but that is > orthogonal to the "marked box detection", which is the part I'm > concerned with here. > > Does anyone have advice, or sample code, on how to approach the first > part, the alignment? I think I understand enough to do the remaining > parts, as well as understanding how to generate the form that would be > printed to be the answer sheet. > > Or maybe this is a solved problem, that I have missed in my searches. I > found lots of paid solutions to this sort of thing, but didn't find a > freeware, or low-cost shareware, but maybe there was one hidden in the > noise. I'm not averse to using something besides ImageMagick if it > exists as a canned solution, but if I need to create my own, then > ImageMagick seems like a good starting point overall, and if I can > figure out how to do the scan alignment. > > Glenn > _______________________________________________ > Magick-users mailing list > [email protected] > http://studio.imagemagick.org/mailman/listinfo/magick-users > > _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
