Linux tip: Creating a pixel ruler from the command line

“Sometimes I need to draw a few lines or some text on an image
or a blank canvas. Just recently I needed to include a simple image
of a pixel ruler in a developerWorks article. I wanted the image to
be 572 pixels wide, to match the current recommended maximum for
developerWorks article images as described in “Illustrating your
article or tutorial for developerWorks.” Lots of on-screen pixel
rulers are available for Linux and for Windows (see Resources), but
I just wanted a simple GIF, JPEG or PNG image. This tip shows you
how to use Bash scripting, shell arithmetic, and ImageMagick to
create a pixel ruler. Make a canvas

“The first thing any artist needs is a canvas, so let’s create
one using the XC pseudo image type in ImageMagick. We also need a
color, either one of the many named colors in ImageMagick, or a
custom color. (See Resources for a link to the ImageMagick
documentation, where you can find a full list of pseudo image types
as well as color names.) Listing 1 shows how to make a light blue
572×100 canvas using the convert command. (The convert command is
customarily used to convert to a different image format or
otherwise alter an image.)

“Listing 1. Creating a canvas

convert -size 572×100 xc:lightblue ruler1.gif

“Figure 1 shows our new canvas.”

Complete Story