Poor man's document camera for videoconference | Hacker News Reader

Poor man's document camera for videoconference

info.iet.unipi.it

205 pointslrizzo56 comments

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.

This explanation nails how to do it though: http://www.imagemagick.org/Usage/compose/#divide

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.

Also though, there are tools like https://miro.com and https://beta.plectica.com which kinda make this obsolete for many common use cases.

Google has photoscan app on Android that is pretty good.

Most commercial solutions solve this by using bright illumination from both sides to avoid shadows. In a pinch a couple of led under-cupboard light strips off would probably work. Something like:

https://www.interactive-education.co.uk/product/visualisers/...

It's almost always easier to control the illumination in the first place rather than fix it in post.

In the real world the "bright illumination from both sides" solution is called a makeup mirror. Just get one of those and glue the phone to it.

Notes has a good document scanner on iOS - https://support.apple.com/en-us/HT210336

Google Photoscan mentioned by someone else is also great, it's available on iOS and Android

It takes a series of photos, and guides you to move the phone as the document is illuminated from different angles by the led flash. It then blends them for optimal result to eliminate glare

Notes document scanner for iOs is great. I use all the time.

I'm surprised nobody has mentioned Scannable yet, by Evernote. I use it regularly: it's a simple and pleasant marvel of technology. Free, no account, point your camera at a doc and it somehow recognizes it, snaps a pic and makes it look just like a document scan, no shadow no nothing. Share as PDF or image. Miles ahead of Apple's "import scan from iPhone" feature, even though it predates it.

I don't have an Evernote account but I'd definitely pay a few bucks for this app if they pulled up a paywall.

I really rate Microsoft's free Office Lens for document scanning. It automatically crops and there are a few filters you can experiment with to get the best result and the output to PDF or whatever.

iOS: https://apps.apple.com/gb/app/microsoft-office-lens-pdf-scan... Android: https://play.google.com/store/apps/details?id=com.microsoft....

For Android there are few fully free & open-source alternatives.

I use OpenNoteScanner.[0,1]

[0] https://github.com/ctodobom/OpenNoteScanner

[1] https://github.com/yeyeto2788/OpenNoteScannerPDF

I have had good success with the document scanning built into iOS. For some reason it's buried within the Notes application.

MS OL works surprisingly well with OneDrive on my iPhone. I frequently use this pipeline on my desktop instead of using my USB printer/scanner.

I've also used OL on Windows 10 (desktop) to crop images of documents sent to me from others. The GUI assumes you're using the app on a tablet, but it's workable.

I don't like the recent update to OL which added a carousel of images from my iPhone's stored photos. I use OL exclusively for business, so the carousel showing personal photos is idiocy.

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.

https://mhenr18.github.io/improvised-document-camera/

I don’t want to look like promotional, but recently a professor used an Osmo reflector (https://twitter.com/romps/status/1237617042338897921?s=12) to project class notes and it caught on with teachers.

A team worked through the weekend and released a free app to make this super easy (https://twitter.com/PlayOsmo/status/1241152565083090947).

While the base + reflector is not free, if you already have an Osmo game at home, you can reuse that.

OMG, this is exactly what I needed! I've been working from home for five years, and the one big missing piece was "whiteboarding".

I even have an extra Osmo reflector and base! Now I just have to convince the kids to stop playing Osmo long enough so that I can use it. :)

Thank you!

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)

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.

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.

If you have to use indoor lighting, find a flat object to lay it on, then tilt it parallel to the light so your hand is less likely to cast a shadow.

> "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."

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?)

Sounds like way less work for those already developing videoconferencing apps than to deploy stand-alone solutions in addition to that.

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.

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.

Hell, it's no wonder Apple can get away selling their expensive stuff, the others aren't really setting the bar high enough...

>> "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." >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?)

Author here.

There have been a few proposals in this space for the past 25 years including hangouts extensions, using a virtual camera that just exports the screen (if people remember the old mbone tools wb and vic; I myself wrote an extension to replace the camera with a snapshot from a configurable region of the X screen), and my own shared whiteboard which gives parties a shared screen that they can edit modify replay ...

http://info.iet.unipi.it/~luigi/wb/

There are two main reasons (in my opinion) why this space has been neglected:

- almost nothing matches the convenience, speed and _resolution_ of writing and drawing with an actual pen. Pads with sufficient resolution and decent lag are only appearing now, and they are fragile and expensive. Graphic tablets are cheap but lack the visual feedback and looking at the output on the screen still has significant latency. They are moderately usable, but takes time to get used to them, and you need a real 10+in screen to use them effectively. Using a finger or a conductive pen on a phone screen is only good for small sketches, not for writing longer sentences or formulas.

- the main users of such products would be non commercial entities (pre-college schools, students) so there are no paying customers. Even at college level lectures are increasingly based on slides prepared in advance. Businesses, of course, use slides or meet in person, and the whiteboard style of collaboration is generally done in person.

Social distancing now may actually create more use cases and perhaps returns (in terms of actual money or social appreciation) that stimulate software solutions to appear.

The Apollo13 problem still stands: even if we had good and cheap technology for writing, at this time it would be impossible to build and sell such products to customers, so we have to find solutions that use hardware already in possession of the users.

> "almost nothing matches the convenience, speed and _resolution_ of writing and drawing with an actual pen"

Absolutely agree, which is why I think attempting to reproduce that convenience on a digital system would be the wrong assumption to begin with. Pen and paper are special.

I think the issues you described in combination to the original solution I mentioned could be mitigated by dynamically increasing the image size. So instead of viewing the screen as your entire whiteboard, it grows as you add more drawings/notes to it. So for example, you have the phone and the white drawing board screen, you scribble f(x) = on the entire horizontal surface (thus circumventing the inherently low resolution issue of most touch-screens) and then the image width doubles and shifts your view to the newly created whitespace, and so on.

It's not a perfect solution, but I think it could and believe it would lead to the same desired results. It's a compromise between human convenience and adaptation to (pre-existing) physical machine restrictions.

On the topic of financing... maybe crowdfunding, then?

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: https://qz.com/1811768/coronavirus-lockdown-ignites-an-old-i...

Related Note: Referring to this method as poor man's method while using a pack of pasta while pasta is as hard to get as TP. Pun intended?

(unipi.it: University of Pisa)

Also, smooth pasta is embarassing.

that's why they're using it for something else than meals :)

A stack of books with a couple of rulers under the top one works better - it's height-adjustable.

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.

There are actually a whole lot of cheap products based around the phone-as-document-camera idea, e.g. https://www.aliexpress.com/item/4000309823825.html, a stand, phone holder, and ring light.

> 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.

Ways to go even better:

- Don't use an "<x>FPS" based model of continuous transmission - the paper isn't always updating by default

- In extremely low-bandwidth situations, never update while there's a hand in the frame; only update once the paper image settles again

- 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

- 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 at least a dozen degrees.

On my 11 Pro it doesn't change until ~40 degrees of attitude.

In Android there's an option to lock orientation.

There's one in iOS as well.

Only for portrait mode. Never made sense to me why they only allow locking in one orientation and not landscape.

It's "lock rotation", not "lock portrait". If you have the device in landscape when you lock it, it will lock in landscape.

I just did it on an iphone 6S Plus and an iPhone XS both with ios13+, and while in landscape, if I press lock rotation, it changes to portrait and then locks it.

I’ve experienced this since iPhone 3G or iPhone 4, so I assume this is how they have designed it.

https://discussions.apple.com/thread/8237975

This website shows a workaround for it:

https://www.igeeksblog.com/how-to-lock-rotation-in-iphone-la...

No, the feature is called "Portrait Orientation Lock" - it will only lock it in portrait mode and not landscape.

https://support.apple.com/en-us/HT204547

I believe it is either "force portrait" or "autorotate", there is no "force landscape".

You flip it landscape and turn off autorotation.

When my phone was updated to Android 9, that toggle became force-portrait. If I enable it now, it immediately turns back to portrait and disables rotation.

I'm on AOSP Android 10 and it works as I described. Can't remember the behaviour on 9. Have a good one.

From Android 10 or maybe 9 on the side of the soft keys bar appears a little rotation icon when you flip the device.

Found the explanation: https://9to5google.com/2018/03/07/android-p-rotation-button-...

Not all video apps respect the lock orientation setting

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.

https://www.ipevo.com/products

Thank you HN for this article and the comments.

Years ago I wrote a little java command line tool based on BoofCV (Pure Java CV lib - https://boofcv.org/), 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.

I used a combination of Thresholding and deskewing to improve my Documents (e.g. Sauvola, Nick) - see https://boofcv.org/index.php?title=Example_Thresholding

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.

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.

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.

Had to look this up, neat: https://www.kickstarter.com/projects/limemouse/scanbox-turn-...

Bonus points if someone can sell this feature within a notebook/tablet stand. Modifying a tiny tower stand (https://tinytowerstand.com/) comes to mind.

That‘s a really cool idea, does not need much space when not used :)

Hi guys, founder of AWW (https://awwapp.com) 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.

"Apollo 13 style camera stand"

That name sounds amazing for being a box of pasta!

Fine until you eat up all your other pasta. Then where are you? Well, I guess at that point you have bigger problems. :)

Just cut a slit the shape of the cardboard profile in the top of the pasta box and shove the cardboard in?

You would still need to fill the box with something heavier than pasta.

What's more valuable: The box of pasta or the roll of coins providing a counterweight?

That's what I thought. Surely you could buy 10 professional document cameras for the value of that pasta! :-)

At least this design doesn't need TP.

Never in my life would I have imagined that toilet paper is rarer and more valuable than boxed pasta.

I think he goes for the inexpensive solution. He could have used toilet paper as foundation :)

They're the smooth (lisce) penne, not the furrowed (rigate) variety. "nobody" uses those!

At the start of the quarantine, when Italians went and stripped shops bare of goods despite all warnings about the supply chain being in no danger and there being no need to stock up on everything, this type of pasta was the only one left on most shelves.

The reason for that _might_ have to do with the "fact" that it's more difficult to ensure pasta sauce sticks to the smooth type - the grooves help a LOT ensuring the sauce sticks well and homogeneously.

As to why people would leave any type of food on shelves if they were truly thinking they'd need to stock up... I've no clue.

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