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PODetecting empty pages in scanned documents
 

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    <p>So we need to detect whether an image, created by a scanner, represents an empty page. I'm way out of my depth when it comes to image processing, so I have to run this by the community. </p> <p>Here's what I have come up with so far: </p> <ul> <li><p>Empty pages can be glaringly white, gray recycled paper, or yellowed old paper. The current idea is to create a histogram for a page, look for a steep increase of the curve, and get the percentage of pixels are darker than that. If that exceeds a threshold, the page is likely not empty. </p></li> <li><p>Since this would likely classify a page containing a single line of text at the top as empty, we would tile the page and gather statistics about each tile. </p></li> <li><p>We would need to detect scanned staplers and holes from binding (likely only in certain tiles), but this can be put off to some later stage. However, if you have an idea what to look out for besides these two, please mention it in a comment. </p></li> <li><p>This needs to be fast. It's part of a document processing workflow that processes (tens of) thousands of pages per day. If processing a page takes ten seconds longer, than our customers will have to tell their customers that they'll have to wait several days longer for their results. (If this results in more false positives, some customers would rather have someone check a few dozen found "empty" pages, than have their customer wait one more day.)</p></li> </ul> <p>So here's my questions: </p> <ol> <li><p>Is it a good idea to take this route or is there something better? </p></li> <li><p>If we do it this way, how would I do this? What's a good (cheap) algorithm for finding a threshold for a page? Could we gain significant speed by assuming a similar threshold for a batch of documents? To which precision could brightness values be rounded, before getting logged? What quirks could we expect? </p></li> </ol>
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    1. COInteresting question, +1. Have you considered training some perceptrons or SVMs?
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    2. CO@larsmans: To be frank, I had to look up both terms... Anyway, training isn't something we can do, because we're not the ones processing this data. Training would require our customers to train the system for their customers' data. I'm pretty sure PM would put a lid on that idea the moment they heard it...
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    3. CO@sbi: You don't necessarily need to retrain for each and every client if their datasets aren't extremely different. But doing this right does require some knowledge of machine learning.
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