Size of Alias files

It looks like ALL aliases to a PDF file are 336KBs. The alias is storing a whole lot of information in the Data fork. If your PDF is a couple of MBs then an alias will make sense. If it is smaller than 400KBs you just as well make a copy of the file. Aliases for pngs and jpegs can be in the same range (340KBs), but may well be considerably smaller than the original if the original is in the MBs size range. For smaller original jpegs the alias is less than 340KBs and varies, but is sometimes a tad larger than the small original, and sometimes a tad smaller. Thus a 193KB original produces a 205KB alias. Oddly enough jpegs with a custom thumbnail may actually produce a smaller alias than jpegs without, even though those with a custom thumb have an alias with BOTH a data fork and a resource fork, while those without a custom thumb only have a data fork.

I know that in Leopard if you made an alias to a folder that had a system icon the resulting alias could well be larger than the original folder with all its contents. This was because the alias was storing the large 512x512 icon, that many system folders had, within itself, while the original folder didn't need to, since Finder displayed the icon from the resource folder where such things were kept. Making an alias of a folder that you had added a 128x128 icon to was much smaller. Whether something similar is happening in Snow Leopard I don't know, but suspect that is the case. Thus I created a new folder, completely empty with the default generic icon, and the alias is 1MB! Creating a new folder and then using GetInfo to add a very small custom icon to it, and then making an alias of it, I get a 16KB alias file. My guess is it is all about icons.
Francine


Francine
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