I wanted to crop out a specific rectangle in a few dozen scanned documents with ImageMagick like this:
```bash
convert -crop 1600x1880+100+420 image.nrm.png cropped.png
```
Scanning often results in a tiny skew, which would lead to a slightly different rectangle location on every image. It seems that a common preprocessing step when doing OCR is to automatically correct this skew. The Python toolset ocropy ((<a href="https://github.com/tmbdev/ocropy">https://github.com/tmbdev/ocropy</a>)) for example contains a tool to do this: `./ocropus-nlbin image.jpg` creates the file `image.nrm.png` which is optimized for OTR and has corrected skew.