1. Icons in OSX are bitmaps, not vector images. (They have been rendered from vector/3d source files, since Apple frequently has them printed at enormous sizes for promotional purposes.)
2. The two key things to bear in mind when creating alpha-channelled images are:
a. Make sure you have a high quality mask
b. Make sure that the image has not been premultiplied against a background color -- often black (Max 4.2 certainly does this to its renders, later versions may also do this).
To correct a premultiplied image, the best option is to figure out how to stop producing images that are premultiplied; alternatively, you can open the image in Photoshop and then (once you have separated the image from its background) you can "remove white matte" or "remove black matte" from the Layer menu.
If you have an image rendered against a white or black background, you can matte it properly in Photoshop by using the Magic Wand tool (tolerance 0, antialiasing ON) to select the backdrop, invert your selection, new layer by CUT, and destroy the old layers. Then remove white/black matte, and save as PNG.
Photoshop 8 a.k.a. CS seems to have some smarts when it comes to removing premultiplied mattes, so if you're using the latest version of Photoshop all these instructions may be redundant.
2. The two key things to bear in mind when creating alpha-channelled images are:
a. Make sure you have a high quality mask
b. Make sure that the image has not been premultiplied against a background color -- often black (Max 4.2 certainly does this to its renders, later versions may also do this).
To correct a premultiplied image, the best option is to figure out how to stop producing images that are premultiplied; alternatively, you can open the image in Photoshop and then (once you have separated the image from its background) you can "remove white matte" or "remove black matte" from the Layer menu.
If you have an image rendered against a white or black background, you can matte it properly in Photoshop by using the Magic Wand tool (tolerance 0, antialiasing ON) to select the backdrop, invert your selection, new layer by CUT, and destroy the old layers. Then remove white/black matte, and save as PNG.
Photoshop 8 a.k.a. CS seems to have some smarts when it comes to removing premultiplied mattes, so if you're using the latest version of Photoshop all these instructions may be redundant.