note 106093 added to function.imagepng

The name "quality" for the compression parameter is quite misleading, as png compression is always lossless. The trade off is between speed and filesize, it cannot affect quality. Here's something I found at stackoverflow; I haven't checked it, but if it is correct it should definitely included in the documentation: --- from php source (gd.h): /* 2.0.12: Compression level: 0-9 or -1, where 0 is NO COMPRESSION at all, * 1 is FASTEST but produces larger files, 9 provides the best * compression (smallest files) but takes a long time to compress, and * -1 selects the default compiled into the zlib library. */ Conclusion: Based on the Zlib manual (http://www.zlib.net/manual.html) the default compression level is set to 6. --- Regarding suggestions to rescale the 0-99 quality range of jpeg into the 0-9 range of png, note that for jpeg 99 is minimum compression (maximum quality) while for png 9 is maximum compression (quality doesn't change). ---- Server IP: 130.206.1.5 Probable Submitter: 80.58.205.96 (proxied: 88.20.71.86) ---- Manual Page -- http://www.php.net/manual/en/function.imagepng.php Edit -- https://master.php.net/note/edit/106093 Del: integrated -- https://master.php.net/note/delete/106093/integrated Del: useless -- https://master.php.net/note/delete/106093/useless Del: bad code -- https://master.php.net/note/delete/106093/bad+code Del: spam -- https://master.php.net/note/delete/106093/spam Del: non-english -- https://master.php.net/note/delete/106093/non-english Del: in docs -- https://master.php.net/note/delete/106093/in+docs Del: other reasons-- https://master.php.net/note/delete/106093 Reject -- https://master.php.net/note/reject/106093 Search -- https://master.php.net/manage/user-notes.php