[neil_swann80]

I wrote a batch script to simplify the ImageMagick conversion. Here's the code in case anyone finds it useful:

@ECHO OFF
TITLE Magick Bulk Convert

Setlocal EnableDelayedExpansion

SET /a i=0
SET /a j=0

::Sets working directory and creates output directory
%~d1
CD "%~p1"
IF NOT EXIST converted MD converted

::count images
FOR %%a in (*.png,*.jpg,*.jpeg,*.gif,*.bmp,*.webp) DO SET /a i+=1

::perfoms convert and calculates percentage done
FOR %%a in (*.png,*.jpg,*.jpeg,*.gif,*.bmp,*.webp) DO (
	magick convert %%a -gravity center -crop 3:4 -adaptive-resize 1072x1448^^! -colorspace gray -colors 16 converted\%%~na.bmp
	SET /a j+=1
	SET /a done=!j!*100/%i%
	CLS
	ECHO.
	ECHO Converting Images - !done!%%
	)
CLS
ECHO.
ECHO Process complete!
ECHO.
PAUSE

Obviously you need to have ImageMagick installed.

Save the text above into notepad, then rename from .txt to .bat

Place the batch script in a folder with the images you want converted, running it will convert images (bmp, gif. jpg, png, webp) to a grayscale 4-bit bmp image. It will also center-crop to a portrait 3:4 aspect ratio, before setting the final resolution (currently set for a HD3, but just edit the code to the resolution for your own device).

The batch script creates a folder called "converted" (in the directory the batch file is run from) and outputs to that folder. The batch file displays a percentage completion whilst running.