imagemagick
Convert jpg to png.
convert image.jpg image.png
convert image.jpg -quality 50 image.jpg
‘Quality’ must be from 1 to 100.
convert -resize 50% image.jpg image2.jpg
Resizing only changes jpegs. Change a png with:
convert input.png png8:out.png
Invert Colours
convert input.jpg output.jpg -negate
Make Images Smaller
convert image.jpg -resize 25% output.jpg
Trim images to border
This is generally used for transparent images.
convert -trim image.png output.png
Make the white of an image transparent.
convert -transparent white -fuzz 10% input.png output.png
The ‘fuzz’ option tells the computer that ‘close to white’ is fine. You might want to use 20% or higher fuzz.
Dropshadow
`convert <input file> \( +clone -background black -shadow 50x8+0+5 \) +swap -background none -layers merge +repage <output file>`
Convert every jpg in directory to png
mogrify -format png *.jpg
Printing Words
Mass convert
This script converts all jpg files in a directory to svg.
for i in *jpg
do convert "$i" $(ls "$i" | sed s#jpg\$#svg#)
done
SVG
The above script has crappy results. It’s better to use potrace.
$convert -flatten input.jpg output.ppm
$potrace -s output.ppm -o svgout.svg
Writing Words
See your installed fonts:
convert -list font
Make an image showing day of the week:
convert -fill blue -font Sauce-Code-Pro-Semibold-Nerd-Font-Complete-Mono -gravity center -pointsize 79 label:$(date +%A) day.png
Make a meme:
convert inputmemeimage.png -font impact -fill white -pointsize 84 -stroke black -strokewidth 3 -gravity north -annotate +0+20 'TOP MEME TEXT' -gravity south -annotate +0+20 'BOTTOM MEME TEXT' outputmemeimage.png