How can you tell png8 from a png24

Question

I'm working on a website that uses lots of png24 files, for transparency.

I need to replace them with png8 files, as all the png fix style javascript workarounds for png24 cause IE6 to lock up randomly.

See this link to get an idea of the symptoms IE6 displays - http://blogs.cozi.com/tech/2008/03/transparent-pngs-can-deadlock-ie6.html

Does anybody know an easy way of targeting existing png24 files, to replace them with the png8s?

I'm using a OS X, and file browsers like Adobe bridge don't show this, nor can I find the info on the commandline, or the finder.

Help!

Answer 1

The file utility on OSX can tell you the colour depth in a PNG file, e.g:

% file foo.png 
foo.png: PNG image data, 1514 x 1514, 8-bit grayscale, non-interlaced