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Running a high trafficed platform. In my quest to minimise bandwidth costs, I added a high JPEG compression on all JPEG uploads (check solution in my previous question). However, Wordpress does not convert PNG files to JPEG, which means that all PNG files remain at their original size.

Is it possible to make all PNG uploads be converted to PNG-8 format? PNG 8-bit is limited to 256 colours which should bring down the file size quite drastically.

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PNG-8 isn't always smaller than PNG24, actually. Furthermore, complex images look real bad at 256 colors (internet c.1995 kinda bad). My recommendation would be to leverage a CDN like Amazon S3 or Rackspace Cloud Files. Bandwidth is cheap and there are plugins which automatically integrate these CDNs for you. – Matthew Boynes Dec 8 '12 at 18:04
PNG-8 will look like a GIF, or not? If not CDN, try to hack into WP image conversion with this library: phpthumb.sourceforge.net – brasofilo Dec 8 '12 at 19:19

If you are trying to optimize the images uploaded, I would try using this plugin http://wordpress.org/extend/plugins/wp-smushit/ I use it on my image heavy sites to upload all past and future uploaded images.

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