Imagemagick Text Placement on Images with Varying Dimensions

Question

I want to be able to overlay text in the margin of images with varying dimensions. Images of varying dimensions will have a black margin that is 30% the width of the image.

I have the following bash script:

#!/bin/bash

command -v convert >/dev/null 2>&1 || { echo >&2 "I require convert, but it's not installed. aborting!";exit 1;}
command -v identify >/dev/null 2>&1 || { echo >&2 "I require identify, but it's not installed. aborting!";exit 1;}
command -v bc >/dev/null 2>&1 || { echo >&2 "I require bc, but it's not installed. aborting!";exit 1;}

basedir="$(dirname "$(readlink -f "${1}")")"
cd "$basedir"

echo "Please enter your caption and press enter"
read caption

if [ -z "$caption" ]; then
    printf "no caption was selected, aborting!\n"
    exit 1
fi
printf "caption is $caption\n"
if [ ! -d "$basedir"/bakups ]; then
    mkdir -p "$basedir"/bakups
fi
while [ $# -gt 0 ]; do
    file="$1"
    if [ -s "$file" ]; then
        cp -f "$file" bakups
        export imagesize=$(identify -format "%w,%h" "$file")
        export imagewidth=$(echo "$imagesize" | cut -f1 -d",")
        export imageheight=$(echo "$(echo "$imagesize" | cut -f2 -d",")*0.05" | bc)
        convert -background "#0008" -font /usr/share/fonts/truetype/fonts-georgewilliams/CaslonRoman.ttf -pointsize 80 -fill white -gravity east \
        -size $(echo $imagewidth)x$(echo $imageheight) caption:"$caption" \
        "$file" +swap -gravity east -composite "$file" && \
        printf "\n$file watermarked successfully\n"
    fi
    shift
done

It gives me this result:

The text extends past the black margin.

I want the text to stay within the margin, and I want removed that shaded horizontal bar behind the text.

I could tweak the bash script and change the pointsize so that the text stays within the margin, but I want this accomplished automatically without my having to tweak the bash script for images of varying dimensions.

I want the text/margin placement to look like this example below:

Answer 1

I am not an imagemagick expert, but I found it easier to first create the black part using caption: which will do text wrapping for you. Then add the picture of the car (without the black part). I hope this will be enough for you to progress towards the desired solution.

As a starting point, I manually cropped the picture to the car alone, in 3WL51.jpg, size 1650x1232, and used 500x1232 as the desired additional black part.

caption="1925 Ford Model A Touring Car

*

Front Engine Rear Wheel Drive"
font=/usr/share/fonts/liberation/LiberationSans-Regular.ttf
file=3WL51.jpg

convert -size 500x1232 -font "$font" \
 -pointsize 80 -background "#0008" -fill white \
 -gravity center  caption:"$caption" \
 "$file" +swap +append out.jpg