The source file gmagick_methods.c
does not contain an implementation for setCompression
. It appears to only have setCompressionQuality
implemented.
It looks like it was requested at one point and rejected.
[2010-06-19 04:15 UTC] vito@php.net
setImage, getImage and getImageGeometry had been added to Gmagick. The other functions will not be included, consistent with the GraphicsMagick API.
via https://bugs.php.net/bug.php?id=59166
However, there does appear to be a compression type option in the API (also, available in the utility) so I'm not sure when that was added. Maybe you could try reopening the bug?