Mac alias icon changing to default "ico" icon

Question

In an attempt to change the icon of an alias I have copied a PNG image in photoshop (128x128, 64x64, and 32x32). Clicked the alais then "Get Info", selected the icon in the upper left corner and hit paste. The File shows an updated timestamp and the icon changes but not to my intended image.

I've also tried to copy icons from other apps but have had the same result.

An example of the resulting icon

Is this possible? Am I doing something wrong? I know I can use automator to locate a file then open it however I've found some problems running the resulting app on newer versions of OSX.

Background: Mac OS X 10.6.8 however I have access to a machine with 10.8, thanks!

Answer 1

You have to convert that file to ICNS first.

Use img2icns to convert the PNG picture to ICNS, copy the resulting ICNS file and paste it in the same place than before in the "Get Info" window (in the upper left corner icon).