In these situations where you're taking a photograph of writing or a diagram on a piece of paper, it can be surprisingly tricky to get rid of the shading from the lighting conditions and be left with just the content on the page in high contrast.<p>This explanation nails how to do it though: <a href="http://www.imagemagick.org/Usage/compose/#divide" rel="nofollow">http://www.imagemagick.org/Usage/compose/#divide</a><p>Divide a blurred copy by the original and you end up with effectively an adaptive-normalize filter where the result is nice and clear with the shadows and uneven lighting left behind.<p>Also though, there are tools like <a href="https://miro.com" rel="nofollow">https://miro.com</a> and <a href="https://beta.plectica.com" rel="nofollow">https://beta.plectica.com</a> which kinda make this obsolete for many common use cases.
I couldn't resist trying this and making some more detailed instructions for getting better images out of iOS. Turns out that you can get fairly good results without any fancy software.<p><a href="https://mhenr18.github.io/improvised-document-camera/" rel="nofollow">https://mhenr18.github.io/improvised-document-camera/</a>
I don’t want to look like promotional, but recently a professor used an Osmo reflector (<a href="https://twitter.com/romps/status/1237617042338897921?s=12" rel="nofollow">https://twitter.com/romps/status/1237617042338897921?s=12</a>) to project class notes and it caught on with teachers.<p>A team worked through the weekend and released a free app to make this super easy (<a href="https://twitter.com/PlayOsmo/status/1241152565083090947" rel="nofollow">https://twitter.com/PlayOsmo/status/1241152565083090947</a>).<p>While the base + reflector is not free, if you already have an Osmo game at home, you can reuse that.
When I use my phone camera to copy documents or especially photographs (i.e. old school printed-on-paper paper photos), I've found the most useful thing is to light it with the sun. You can do it next to a window if the sun is shining in (best the window is clean), or I just do it on my porch if it isn't windy. They come out with excellent quality...I have found it does better than even scanning them (which takes much longer)<p>Obviously, the sun should be at enough of an angle so it won't cause glare. You can try to position it so the sky isn't reflecting in the photo, but honestly the effect of that is going to be miniscule because the sun is so much brighter.<p>And of course, if you have to do it when the sun isn't out, you can make do with whatever lighting you have, but the quality won't be as good from my experience. I've done this for family photos from ages ago, and it wasn't a problem to wait for some sunshine.
> <i>"With so many people and students around the world working from home, we really need some easy to deploy shared whiteboard solution. This is especially important for pre-college students who may not have access to high end hardware."</i><p>Just add a new mode to videoconferencing, where both parties get a white screen and both can start drawing and the resulting image stays in sync on both clients? (I feel like this solution is so obvious, I'm about to fly out a window - what am I missing?)<p>Sounds like way less work for those already developing videoconferencing apps than to deploy stand-alone solutions in addition to that.<p>In fact, phones could do good just having a "scratchpad" as a "phone-variant" of Notepad and/or Paint. It helps to quickly draw something, a simple sketch, or communication with deaf people or those who don't share a common language.<p>It's sad to see the state of bloatware on phones and not seeing many useful things. It took ages for them to add the torch/flashlight feature as a standard into the OS, back in the day, we needed to use apps to get that done, so I think it's probably symptomatic of the entire industry.<p>Hell, it's no wonder Apple can get away selling their expensive <i>stuff</i>, the others aren't really setting the bar high enough...
Off topic, but as OP is from the .it TLD, it’s interesting to note OP prefers riga pasta, especially in light of this article: <a href="https://qz.com/1811768/coronavirus-lockdown-ignites-an-old-italian-debate-its-about-pasta-of-course/" rel="nofollow">https://qz.com/1811768/coronavirus-lockdown-ignites-an-old-i...</a>
A stack of books with a couple of rulers under the top one works better - it's height-adjustable.<p>Moving a bit further up the quality ladder, I've just built myself a solid laptop/monitor stand out of plywood, and I'm going to attach a strut sticking out the back to hold up a webcam-as-document-camera and (when it arrives) an LED ring light.<p>There are actually a whole lot of cheap products based around the phone-as-document-camera idea, e.g. <a href="https://www.aliexpress.com/item/4000309823825.html" rel="nofollow">https://www.aliexpress.com/item/4000309823825.html</a>, a stand, phone holder, and ring light.
> <i>frame rate, encoder quality. Especially low end phones do not have enough power to encode highly variable input (see previous bullet), resulting in unreadable images. An encoder setting for low frame rate (e.g. 1-2FPS) and high quality would be invaluable for such an use case.</i><p>Ways to go even better:<p>- Don't use an "<x>FPS" based model of continuous transmission - the paper isn't always updating by default<p>- In extremely low-bandwidth situations, never update while there's a hand in the frame; only update once the paper image settles again<p>- Get all fancy with feature detection and draw buttons on the corner of the paper; one of these could be "update" and the device would beep to acknowledge the frame had changed. This is actually practical as not everyone has bluetooth keyboards, audio-based commands would be distracting, and tapping onscreen buttons would nudge the device<p>- Perform frame border analysis and automatically crop and rotate the actual paper as it's moved around
Re. orientation: the phone shouldn't be trying to determine landscape/portrait when flat; it should gracefully keep the previous state for <i>at least</i> a dozen degrees.<p>On my 11 Pro it doesn't change until ~40 degrees of attitude.
If you want to upgrade from DIY, Ipevo sells a line of document cameras that start at $99. Some are not as expensive as dedicated, stand alone classroom document cameras because they require a computer to operate.<p><a href="https://www.ipevo.com/products" rel="nofollow">https://www.ipevo.com/products</a>
Thank you HN for this article and the comments.<p>Years ago I wrote a little java command line tool based on BoofCV (Pure Java CV lib - <a href="https://boofcv.org/" rel="nofollow">https://boofcv.org/</a>), tess4j (tesseract) and PDFBox to create PDFs with OCR and invisible Text Layer, to make its contents searchable like the OCR Option in PDF X Change Viewer.<p>I used a combination of Thresholding and deskewing to improve my Documents (e.g. Sauvola, Nick) - see <a href="https://boofcv.org/index.php?title=Example_Thresholding" rel="nofollow">https://boofcv.org/index.php?title=Example_Thresholding</a><p>Now I plan to restore and improve the old code and provide it as open source solution :-) Hope the code still somewhere on my old harddisks.
Reminds me a kickstarter project I backed years ago called ScanBox. I still pull it out from time to time to scan documents when traveling, and have used it once or twice for a live document scanner, though the sides of the box make it difficult to get your hand into.<p>These days our team either uses the built-in whiteboard functionality in Zoom, or jump into a Google Drawing or Slides document for the live collaboration.<p>Sometimes I'll also use Zoom's AirPlay functionality to share my iPad screen and use an app like Notability to share. Though that's only one-way and not collabarative.
Hi guys, founder of AWW (<a href="https://awwapp.com" rel="nofollow">https://awwapp.com</a>) here. AWW is one of the first and simplest online whiteboard on the market. Check us out. Also, for schools, we are giving free premium until the end of the COVID-19 situation. Stay safe everyone.
I use a pile of book with the mobile phone on the top of them. For photos I use CamScanner free because it crops automatically the photo, auto contrast them and save multiple pages as a pdf.