I usually scan all my documents with a flatbed scanner that I have at home. It also has an automatic document feeder, which is a blessing for long documents. Sometimes I want to scan something on the go. Usually I just take pictures with the camera app, but as there are many apps out there, I wanted to see whether I could find something good.
As a benchmark, this is the result that I get from the flatbed scanner and adjusting the levels with GIMP:
There are no shades, no wrinkles. It looks reasonable. This is a hard example as it is thermographic paper and crumpled in my wallet. But still, why not take a challenging example? By the way, without software post-processing, the result looks rather bad:
So how does my phone compare to that?
First we need to use the normal camera app and take a picture of it. With cropping it and applying the automatic improvement on Google Photos, we get the following:
One can see that it is already blurry and has some shade from the creases. Trying to improve this in GIMP using the levels was not very fruitful:
It is okay, one can read it, but that's not great.
This first app is really easy to use. It does not seem to want any data. It lets you take pictures and that is about it. It automatically tries to find the document, lets you do some black and white conversion using some preset thresholds.
In the end you find a JPEG file for each of the pages in a directory structure. And the result looks very reasonable. Interestingly the resolution of the image is about the same as I have set on my flatbed scanner (300 DPI).
I believe that the PDF generation is a paid feature, but I am happy with JPEG files and use ImageMagick to generate PDFs from that.
Although I am wary of Adobe products, I have tried their scanning application. It automatically detects a document and takes the picture when it has found one. Alternatively one can just take the picture manually. It offers the same cropping.
My problem with the app is that all documents get uploaded into the Adobe Document Cloud by default. One has to then download them to the device in order to use them somewhere else. This is not exactly what I want.
The scan result is okayish. I actually could not find an option for just black-and-white, I can get grayscale, but that does not look as nice as real BW.
I wanted to try Mobile Scanner, as it was advertised on top of the list in the Google Play Store search. However, the fact that it wants to transmit my image content to their service. And also it would cost me to use the app.
Well, I haven't pushed any further with this one.
The next app looked promising. It features the usual picture taking, cropping and so on. In the result one can select whether it is a document or it should have some magic “clear” filter.
The result is okay, the Simple Scanner had it much better, I think.
Microsoft Office Lens
The last one that I have tried is the Microsoft Office Lens. It also has a privacy statement. But in the end it lets me choose whether I want the pictures in the gallery, a PDF file on the device and then also exports to various Office products. I really like this choice!
I have chosen the “clear” filter for the end result. There is a gray shade on top of it, the others do not have it. But there are no shadows. Their BW filter looks rather the same, so it did not make any difference, really.
I find it amazing that these apps can extract the actual content and remove the shade. I am not sure how exactly they do that, might be with machine learning. Either way it is something that I cannot simply do with a threshold or level adjustment in GIMP. I prefer the Simple Scanner application and will continue to use that for scanning on the go.