resize a picture in osx

If you don't have Graphic Converter or a similar program, the easiest way will be to Import it into iPhoto (by dragging and dropping), then Export it back out to the size you need by choosing the right option from the iPhoto menus.

 

Another nice, free alternative is Seashore.

 

When you choose the Export option, it will prompt you for the image format and the size you want to export to in pixels. The actual Export window varies depending on your iPhoto version, but it tends to use the term "scale" rather than resize. Make sure you choose either the JPG or PNG format too.

 

Automator

I use a automator action, create a new action, Preview has a action that allows you to resize a image... works like wonders, no downloads and free as can get!