First Plugin dev question

OK, I am about to try my hand at writing a plugin. To start simple I am going to wrap EE’s imagelib so that you can get image properties in your template code.

I envision usage like this: {exp:img_prop img_url="http://site.com/path/to/image.jpg"} width = {width} height is {height} … {/exp:img_prop}

So, I think I only need one function (the main class) and in there I call the imagelib stuff then with a switch statement, put the relevant data in $TMPL->tagdata via swap_var_single.

Does that sound about right?