On the Mac, application icons are stored in the .icns (Mac Icon File) format, as a number of images in sizes up to 512×512px (this is a new standard in Leopard). In this tutorial, we will learn to create a Mac icon.
I’ll assume that you already have your images in PNG format. You can create these images yourself using a graphics application such as Photoshop, or you could find existing images from the internet. (Remember to respect copyright, but for personal use it shouldn’t be an issue.)
To turn your images into an icon, I recommend Apple’s own “Icon Composer” program. This software is available in the Developer folder if you installed XCode Tools when you got our computer. Otherwise, you will find the XCode tools on your Leopard Install DVD under “Optional Installs”.
As you can see below, using this software is simple. Simply drag the various images for the icon into the box corresponding to their size, and select the copying option you want.
If you don’t have an image for some of the sizes, the option “Copy to all smaller sizes which are empty” will fill in the gaps. You can create an icon using a single 512×512px image, but if you want the image to remain clear in smaller sizes, it is best to fix them up by hand.
That is what separates icon amateurs from the pros!
You can find a great article about the importance of doing this at mantia.me.
If you select “Preview” from the bottom of the Icon Composer window, you can see how your icon is going to look at different sizes, to see if you need to fix anything up.
This free application, available here, provides a quicker and easier way to create an icon. It does not provide support for different sizes, having the same effect as the Icon Composer option “Copy to all smaller sizes”. Simply drag an image onto the application, and your icon is created.
This application will be especicially useful for those who do not want to install the (rather large) XCode Developer Tools application set.
If you have any questions, feel free to ask them here. Have fun creating your icons!