Scripted Multiple Resizes With ImageMagick

The problem: A friend had taken a screen capture and was having difficulties getting it to display nicely in WordPress.

An interesting challenge I thought to myself. I know I can use all sorts of funky resize filters with ImageMagick, but which one would work best? A few clumsy minutes later, I had an answer, but that in turn raised another. Just editing the command history is fine and dandy, but there must be a better, faster, more efficient way!

Surely I can script something that will generate all the variants in a single go???

And there surely is:

for i in `convert -list filter` ; do \
    echo $i ; \
    convert -filter $i -resize 563x367 \
        -pointsize 20 \
        -draw "fill black text 40,42 $i fill white text 41,41 $i" \
        custom-advanced-a-and-b.png \
        converted/$i.png \
; done

This (effectively) one liner shell script:

• Loops over the various filters that recent versions (v6.3+ ??) of ImageMagick can process.
• Displays the current filter being used to the console. The equivalent of seeing an hour-glass.
• Applies that filter to the resize operation.
• Puts in a 20 point sized watermark into the image. The watermark text being the filter used. Because I could.
• Writes this new image out into a subdirectory (converted) with a new filename being the filter.

It is then extremely easy to use an image viewer and rapidly page between the new versions.

Once a filter to use has been chosen? Just run the convert command with that single filter only, and minus the -draw stuff.

convert -filter Hermite -resize 563x367 custom-advanced-a-and-b.png custom-advanced-a-and-b.SMALL.png

Easy!