Work the Shell - Resizing Images, Sort Of

Here's the basic script at this point:

filename="edit.png"
multiplier="0.75"

width="$(file $filename | cut -f5 -d\  )"
height="$(file $filename | cut -f7 -d\  | sed 's/,//')"

width="$(echo "$width * $multiplier" | bc | cut -d. -f1)"
height="$(echo "$height * $multiplier" | bc | cut -d. -f1)"

echo "$filename scaled: width=$width height=$height"

Testing it with the filename specified produces the following:

$ sh scale-image.sh
edit.png scaled: width=541 height=539

That's not really exactly what I want, however. First, I want to be able to specify the filename and multiplier on the command line. Second, the output needs a slight tweak to be more useful—the values need to be surrounded by quotation marks.

Here's what I'd like to see:

$ sh scale-image.sh 0.75 edit.png
edit.png: width="541" height="539"
$

That's not too hard to accomplish given the basic script we already have. See if you can do it yourself.

Tip: I actually use a “for name; do; done” loop to step through the file scaling, so I can specify a group of images and calculate them all en masse. Try it, coupled with the shift command, to remove the multiplier value once it's saved into a named variable.