I don’t know how to use imaging software. I mean, I used to use Gimp and Inkscape when I was a more frequent Debian user, but since when I switched to MacOSx, I just stopped. A few days ago I wanted to create a new background image for all python-related posts.
The only package needed is ImageMagick.
1. First I got to find an image labeled for reuse
I used Google Image search labeled for use filter and got pointed to some python wikimedia image. As it is labeled as public domain, I am free to do anything with it :-).
$ wget https://upload.wikimedia.org/wikipedia/commons/a/ab/Python_natalensis_Smith_1840.jpg
$ mv Python_natalensis_Smith_1840.jpg post-bg-python-01.jpg
The “original” image (resized to 20%).
2. Resizing
ImageMagick allows us to resize the image in many ways.
$ convert post-bg-python-01.jpg -resize 1900x600 post-bg-python-01-1900.jpg
$ identify post-bg-python-*
post-bg-python-01-1900.jpg JPEG 1469x600 1469x600+0+0 8-bit sRGB 823KB 0.010u 0:00.000
post-bg-python-01.jpg JPEG 2941x1201 2941x1201+0+0 8-bit sRGB 2.396MB 0.000u 0:00.000
3. Changing colors
Finally, it is possible to negate the colors.
$ convert post-bg-python-01-1900.jpg -negate post-bg-python-01-negate.jpg
The final image.
Real life example
The first post I used this background image was the post about anaconda.