ImageMagick: trim but keep a minimum size

Question

I'm using ImageMagick to trim some PDFs of text that I've converted to jpg for a project. In most cases it works well but when the page has just a small amount of text, say half a sentence, trim works too well so the image is just that, half a sentence.

It's a problem as it causes some display issues where I'm presenting it so it'd be helpful if there was a minimum image size. Is there a way of doing that in ImageMagick? Or adding padding to an image if it is converted below a certain size?

This is the command I'm using:

convert '*.jpeg' -fuzz 1% -trim +repage -set filename:base "%[basename]" "%[filename:base].jpg" 

I'm using ImageMagick 7.1.0-19 Q16-HDRI arm 2021-12-22

Answer 1

Currently there is no way that I can think that would limit the trim in that way in Imagemagick. But you can automatically pad the image with some color such as white to some minimum size.

However, you will need to use "magick" in place of "convert" for Imagemagick 7 to make it work properly.

Input (256x256):

Lets pad it with white to 100x100 (minimum)

magick image.png -fuzz 1% -trim +repage -gravity center -bordercolor white -border "%[fx:w<100?round(0.5*(100-w)):0]x%[fx:h<100?round(0.5*(100-h)):0]" result.png 

or better

magick input.png -fuzz 1% -trim +repage -gravity center -background white -extent "%[fx:w<100?100:w]x%[fx:h<100?100:h]" result.png 

Answer 2

I had the exact same question recently, and the answer was to combine -trim and -extent.

convert -trim -background none -gravity center -extent 1024x1024 input.png output.webp

The image will first be trimmed, then extended to a given size.

You might want to change -gravity and -background depending on your use case.