I don't normally do this, so it took a little hunting, but on the command line, try this:
tesseract input output -c tessedit_write_images=1 You can also use a config file and pass that as the last item on the command line: tesseract input output ~/tessconfig where ~/.tessconfig is a file whose contents are simply: tessedit_write_images 1 -- You received this message because you are subscribed to the Google Groups "tesseract-ocr" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/tesseract-ocr. To view this discussion on the web visit https://groups.google.com/d/msgid/tesseract-ocr/e8c563e3-fbb5-48f8-9f54-c7a360df7178%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.

