Android Question Document scanning

Document scanning usually means that you want to get the text out of the scanned document. Search for OCR if this is your intention.

If you want to transform the document so it will be straight then you should learn about OpenCV: https://www.b4x.com/android/forum/threads/opencv320-for-b4a-v1-0-released.79816/#content

I don't need necessary the text of the document. I just need a scan from the document. If it is slanted then it should adjust and send it like a PDF.
The last step (sending) is the easiest.

Let the user rotate and crop the image.

Erel said:

If you want to transform the document so it will be straight then you should learn about OpenCV: https://www.b4x.com/android/forum/threads/opencv320-for-b4a-v1-0-released.79816/#content

Click to expand...

If the picture is not only XY-rotated but also taken from an angle that is not perpendicular to the document planar surface, there will also be some perspective deformation.
As Erel said, Opencv can be used to detect the contours, then the edges, and 'undo' this XY-rotation and perspective using homography.

Some programming is involved, and reliability will depend on image quality (homogeneus background, avoiding other objects in the picture,...among others)