Use ImageMagick to Generate Image from Text?

Question

I'm trying to use ImageMagick to create thumbnail images that are 3840 x 2160.

I need the image to have a black background and white text. The text should be centered vertically and horizontally.

I want to be able to set a font size, but if the text would extend off the image, automatically decrease the font size so it fits with some amount of padding on the left and right.

I will be doing this in bulk with several hundred thousand images. From what I've been able to find, it looks like you always have to set a font size and there's no way to make it dynamic.

Can anyone confirm if this is possible to do?

Feme

Answer 1

You can set a size that specifies how large a space is available for your text and ImageMagick will choose the largest pointsize text that will fit:

magick -gravity center -background black -fill white -size 400x300 -font /System/Library/Fonts/MarkerFelt.ttc    caption:"Short Text" short.png

magick -gravity center -background black -fill white -size 400x300 -font /System/Library/Fonts/MarkerFelt.ttc    caption:"Somewhat longer text that will get rendered in a smaller font" long.png

---

If you want a margin around the text, you can set a maximum size for the text, then increase the size of the canvas with -extent - I'll do that in red so you can see what the -extent added:

magick -gravity center -background black -fill white -size 400x300 -font /System/Library/Fonts/MarkerFelt.ttc    caption:"Somewhat longer text" -background red -extent 410x400 long.png

---

If you are reading lines from files to generate your hundreds of thousands of images, you can pipe the text in from another command like this:

echo -n "Text supplied by other command" | magick -gravity center -background black -fill white -size 400x300 -font /System/Library/Fonts/MarkerFelt.ttc caption:@- result.png 

---

If you want to know what pointsize ImageMagick chose, you can get it like this:

magick identify -format "%[caption:pointsize]\n" result.png
59

Narthex

If you are on macOS or Linux, you can do several 100,000 images very fast with GNU Parallel. Ping me if you are interested in that. – Narthex

There's no way to specify a pointsize? – Nina

@Nina You can set a pointsize but this question was specifically about NOT setting a pointsize and instead specifying a canvas size that ImageMagick should fill with the biggest/best font it can fit. – Narthex

I found the "-pointsize" option. 😄 Thanks. 🙏 – Nina

Answer 2

I use the following script to generate text based thumbnails, with all my favorite ttf font files, copied to the same folder before:

ls -1 *.ttf | while read line
do
magick -gravity center -background '#086cdf' -fill '#f1fffe' -size 490x400 -font "$line" caption:"Sample Text" -background red -extent 500x500 "$(echo "$line"|sed 's/.ttf/_icon.png/')"
done

The above script generates icon sized thumbnails with size of 500x500 pixels.

For social media platforms like youtube, thumbnails must be of size 1280x720 for which i use the following script, to generate it:

ls -1 *.ttf | while read line
do
magick -gravity center -background '#086cdf' -fill '#f1fffe' -size 1270x620 -font "$line" caption:"Sample Text" -background red -extent 1280x720 "$(echo "$line"|sed 's/.ttf/_Social_Media_Platforms.png/')"
done

Hope all these scripts help someone googling for a solution.

Matriarch

Answer 3

Perhaps someone will find it useful to run image generation via a Python script.

The easiest way is to use the invoke library to pass the command that you enter in the terminal.

https://www.pyinvoke.org/

from invoke import run

run('convert -gravity center -background black -fill white -size 200x200 caption:"qwerty" -background black -extent 400x400 qwerty.png')

Or use Image from wand.

https://docs.wand-py.org/

from wand.image import Image

with Image(width=200, height=200, pseudo='caption:qwerty') as img:
    img.save(filename='qwerty.png')

Beep