For example I made the image with the help of Fuji s6500fd without flash and on ISO400.
Darkly, right? But we can quickly correct this with the command like that:
mogrify -format tif -monochrome -compress group4 -resize 1252x1800 -normalize -threshold 30% *.jpg
You can modify the -threshold option for change the contrast like you want.
The result will be like that:
Of course you can use it method for bath image processing. You can write the script for this very easy.
There you can find a full information about ImageMagick options: