Thread:Project:Support desk/PNG conversion failed; check for correct installation of latex and dvipng (or dvips + gs + convert)

When opening a page with math tag, "PNG conversion failed; check for correct installation of latex and dvipng (or dvips + gs + convert)" (解析失败(PNG 转换失败 ；检查正确安装的 latex 和 dvipng （或 dvips + gs + convert）) in Chinese) is shown.

MediaWiki 	1.21.3

PHP 	5.5.3-1ubuntu2 (apache2handler)

MySQL 	5.5.34-0ubuntu0.13.10.1

I have chmod 777 to wiki/images, and installed dvipng, dvips, gs, and convert.

Here is LocalSettings.php:

which *** are private data.

latex.fmt is in wiki/images/tmp.