As I was previewing my previous entry, I noticed that the thumbnails that WordPress had created for the attached [jpeg] images were of rather poor quality。
in v2.3 it can be improve like this：
but in v2.65 or higher,the default thumbnails quality still very poor.
the code of 2.65 had lots of change, the method for v2.3 is no longer work.
how can improve new version's thumbnails quality with out plugin ?
just fix the code