For the image sample the cam's resolution was been choosen to low, I think.
With the new update of CamScanner, you are able to choose the resolution directly in the app, independent of the system cam's resolution setting.
Open the app, tap on the cam icon, then tap on gear icon, then tap on the resolution icon (right corner).
You might try different resolutions for to find the right one (readable AND file size not to big).
Harry