Use Imagemagick to swap blue and red colors

For a presentation I wanted an image to appear in magenta, rather than in cyan. This is how the image originally looks like:




blue.jgp

With the following command I separated the R, G, B color channels and swapped the Red and the Green channel, to produce a picture in which all blue colors appear in red:

$ convert blue.jpg -separate -swap 0,1 -combine red.jpg

 And that is how the result looks like:




red.jpg


I got this information from: http://www.imagemagick.org/Usage/color_basics/#combine

How to bulk resize JPEG pictures via Imagemagick

Sometimes you need to reduce the size of many pictures, for example to share them on the internet.

A nice way of doing this is via Shell:

convert FILE.JPG -resize 2448x1836 ./smaller_pictures/FILE.JPG

Or by using a for loop:

for F in *.JPG

do

convert $F -resize 2448x1836 ./smaller_pictures/$F
done