How to easy process images previous to OCR?

[Disonantemus]

Problem

I have many documents with images that contain raster images with useful information (like many kinds of charts: organizational, flow, statistics, etc), but images are very different, with many colors/sizes/quality, that get bad results with OCR.

Workaround

Right now, I do:

• Extract the images with pdfimages -all in.pdf _
• Find the correct image
• Process with imagemagick, Example: remove all colors but black (text color) very useful to clean charts/boxes with colors/textures that don't get OCRed): magick in.png -alpha remove -fill white -fuzz 70% +opaque "#000000" -colorspace gray out.png
• OCR with ocrmypdf

I do get a lot better OCR from that (better than use ocrmypdf flags process images).

PROS:

• OCR is better.

CONS:

• Too many steps.
• This is annoying.
• PDF looks worst: the image shown is the one that gets OCRed, not the original one.

Alternative

I know is possible to do a plugin, because #923 , but I don't know how to do that. I'm not a programmer.

Question

There is an easy way to process image(s) inside a PDF with imagemagick (CLI, no python) to manual improve OCR in hard cases?