Get rid of the scale factor

This is a big deal, with pdfminer instead of pypdf, we can read the
image data stream inside the PDF on its original resolution.

I'm expecting much better OCR results now and faster processing.
Simplified some variable names
Remove one more data conversion

Apparently tesseract can take PPMs.
Fix bug when dealing with cities above the Equator line

Sorry for that Amapa. :)