On the site http://www.libgd.org/GdHistory they say:
That "the PNG compression level can now be specified when writing PNG images. See the new gdImagePngEx, gdImagePngEx, gdImagePngCtxEx, and gdImagePngPtrEx functions.".
This feature starts from version 2.0.12.
I have 2.0.35, so yes, libgd should support it.

Thank you,
Andrew

On Wed, Oct 1, 2008 at 6:53 PM, Hans Hübner <hans@huebner.org> wrote:

2008/10/1 Andrei Stebakov <lispercat@gmail.com>:

> I was experimenting with write-png-to-stream trying :compression-level from
> -1 to 9 but it doesn't change the size of the image.
> For jpeg quality level works though.
> What can I check for PNG compression to work?

Are you sure that libgd supports compressing PNGs? If so, it may be a
fixable API problem. Please verify that libgd itself supports
compression, then let us know.

Thanks,
Hans
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