Looking for PNG batch converter

I've had a lot of fun doing animations with "spine" recently. Now I have a huge pile of frames that I want to include in my game. These frames are around 150 kb each. When I simply "save as" and overwrite them in Photoshop (old version: 7) they are magically reduced to around 50 kb. Unfortunately, I was not able to create an automation for that task in Photoshop.

So I've been looking around the web for some time now, trying to find a batch converter that simply makes my png-files a bit smaller. There are tons, but they always convert the PNGs to 8 bit with indexed colours which makes them small (10 kb) but unusable for Visionaire.

Does anyone have a suggestion for a PNG cruncher that keeps the 24bit format?

There is a PlugIn for GIMP, called Davids Batch Processor. If I remember right if you select png as output format you can adjust the compression ratio with a slider.

It works! Perfect! Thank you! :-))

http://pngquant.org/

Its the best and easiest I've found.

But how do you make it produce output for visionaire? I didn't manage to get anything else but 8bit pngs with indexed colours.

have you try to use Actions e Batch in photoshop?
Look this...
http://www.wanlooloo.it/adobe/photoshop/item/modificare-molt...

not tried any of them but maybe something of use in these links...

http://www.smashingmagazine.com/2008/10/02/15-useful-batch-i...
http://sourceforge.net/projects/bulkimageconver/
http://sourceforge.net/projects/dinoimages/

they sound more or less like what you are after.

imagemagick cross-platform and still awesome ;P

you can also try xnview, it has a batch processor with lots of customization options.

Thanks a lot for your suggestions! I'm pretty happy about the gimp solutions now as gimp is part of my actual work flow, but I'll check out the other tools as well.
Your posts might also be a good source of knowledge for other folks dealing with the same problem who find this thread.

glad you got it sorted out!

i use the scripts options in photoshop to do this, there is also a few cool ones that save the placement of the nontransparent images within a png that arent directly touching, and it exports them all to new files preserving the placement

also one that goes through the layers of a psd and can export each layer to a new file, preserving transparency