split_panorama_equally_max_4k.sh

#!/bin/bash

input_image="full.jpg"
output_prefix="part_"
max_width=3840
max_height=2160
aspect_ratio=$(bc -l <<< "$max_width / $max_height")

# Get image dimensions
dimensions=$(identify -ping -format "%w %h" "$input_image")
width=$(echo $dimensions | cut -d' ' -f1)
height=$(echo $dimensions | cut -d' ' -f2)

# Calculate number of parts
num_parts=$(((width + max_width - 1) / max_width))

# Calculate part width
part_width=$((width / num_parts))
part_height=$(bc <<< "scale=0; $part_width / $aspect_ratio / 1")

if [ $part_height -gt $max_height ]; then
    part_height=$max_height
    part_width=$(bc <<< "scale=0; $part_height * $aspect_ratio / 1")
fi

# Split the image
for ((i=0; i<num_parts; i++)); do
    x_offset=$((i * part_width))
    convert "$input_image" -crop ${part_width}x${part_height}+${x_offset}+0 "${output_prefix}${i}.jpg"
done

If errors with image size being too much for convert:

sudo vi /etc/ImageMagick-6/policy.xml

# Modify following, (defaults to 16KP on Debian 12):
  <policy domain="resource" name="width" value="16MP"/>
  <policy domain="resource" name="height" value="16MP"/>