I want to delete / remove all the images in a PDF leaving only the text / font in the PDF with whatever command Line tool possible.
I tried using -dGraphicsAlphaBits=1
in a Ghostscript command but the images are present but like a big pixel.
You can use the draft option of cpdf:
cpdf -draft in.pdf -o out.pdf
This should work in most situations, but file a bug report if it doesn't do the right thing for you.
Disclosure: I am the author of cpdf.