Topic on Project:Support desk

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:

<?php
# This file was automatically generated by the MediaWiki 1.21.3
# installer. If you make manual changes, please keep track in case you
# need to recreate them later.
#
# See includes/DefaultSettings.php for all configurable settings
# and their default values, but don't forget to make changes in _this_
# file, not there.
#
# Further documentation for configuration settings may be found at:
# http://www.mediawiki.org/wiki/Manual:Configuration_settings

# Protect against web entry
if ( !defined( 'MEDIAWIKI' ) ) {
	exit;
}

## Uncomment this to disable output compression
# $wgDisableOutputCompression = true;

$wgSitename = "***";
$wgMetaNamespace = "***";

## The URL base path to the directory containing the wiki;
## defaults for all runtime URL paths are based off of this.
## For more information on customizing the URLs
## (like /w/index.php/Page_title to /wiki/Page_title) please see:
## http://www.mediawiki.org/wiki/Manual:Short_URL
$wgScriptPath = "/wiki";
$wgScriptExtension = ".php";

## The protocol and server name to use in fully-qualified URLs
#$wgServer = "http://localhost";

## The relative URL path to the skins directory
$wgStylePath = "$wgScriptPath/skins";

## The relative URL path to the logo.  Make sure you change this from the default,
## or else you'll overwrite your logo when you upgrade!
$wgLogo             = "$wgStylePath/common/images/wiki.png";

## UPO means: this is also a user preference option

$wgEnableEmail = false;
$wgEnableUserEmail = true; # UPO

$wgEmergencyContact = "apache@localhost";
$wgPasswordSender = "apache@localhost";

$wgEnotifUserTalk = false; # UPO
$wgEnotifWatchlist = false; # UPO
$wgEmailAuthentication = true;

## Database settings
$wgDBtype = "mysql";
$wgDBserver = "localhost";
$wgDBname = "***";
$wgDBuser = "***";
$wgDBpassword = "***";

# MySQL specific settings
$wgDBprefix = "";

# MySQL table options to use during installation or update
$wgDBTableOptions = "ENGINE=InnoDB, DEFAULT CHARSET=utf8";

# Experimental charset support for MySQL 5.0.
$wgDBmysql5 = false;

## Shared memory settings
$wgMainCacheType = CACHE_ACCEL;
$wgMemCachedServers = array();

## To enable image uploads, make sure the 'images' directory
## is writable, then set this to true:
$wgEnableUploads = true;
$wgUseImageMagick = true;
$wgImageMagickConvertCommand = "/usr/bin/convert";

# InstantCommons allows wiki to use images from http://commons.wikimedia.org
$wgUseInstantCommons = false;

## If you use ImageMagick (or any other shell command) on a
## Linux server, this will need to be set to the name of an
## available UTF-8 locale
$wgShellLocale = "en_US.utf8";

## If you want to use image uploads under safe mode,
## create the directories images/archive, images/thumb and
## images/temp, and make them all writable. Then uncomment
## this, if it's not already uncommented:
#$wgHashedUploadDirectory = false;

## Set $wgCacheDirectory to a writable directory on the web server
## to make your wiki go slightly faster. The directory should not
## be publically accessible from the web.
$wgCacheDirectory = "/tmp/cache";

# Site language code, should be one of the list in ./languages/Names.php
$wgLanguageCode = "zh-cn";

$wgSecretKey = "*****";

# Site upgrade key. Must be set to a string (default provided) to turn on the
# web installer while LocalSettings.php is in place
$wgUpgradeKey = "*****";

## Default skin: you can change the default skin. Use the internal symbolic
## names, ie 'standard', 'nostalgia', 'cologneblue', 'monobook', 'vector':
$wgDefaultSkin = "vector";

## For attaching licensing metadata to pages, and displaying an
## appropriate copyright notice / icon. GNU Free Documentation
## License and Creative Commons licenses are supported so far.
$wgRightsPage = ""; # Set to the title of a wiki page that describes your license/copyright
$wgRightsUrl = "";
$wgRightsText = "";
$wgRightsIcon = "";

# Path to the GNU diff3 utility. Used for conflict resolution.
$wgDiff3 = "/usr/bin/diff3";

# Query string length limit for ResourceLoader. You should only set this if
# your web server has a query string length limit (then set it to that limit),
# or if you have suhosin.get.max_value_length set in php.ini (then set it to
# that value)
$wgResourceLoaderMaxQueryLength = -1;


# Enabled Extensions. Most extensions are enabled by including the base extension file here
# but check specific extension documentation for more details
# The following extensions were automatically enabled:
require_once( "$IP/extensions/Cite/Cite.php" );
require_once( "$IP/extensions/ConfirmEdit/ConfirmEdit.php" );
require_once( "$IP/extensions/Gadgets/Gadgets.php" );
require_once( "$IP/extensions/ImageMap/ImageMap.php" );
require_once( "$IP/extensions/InputBox/InputBox.php" );
require_once( "$IP/extensions/Interwiki/Interwiki.php" );
require_once( "$IP/extensions/LocalisationUpdate/LocalisationUpdate.php" );
require_once( "$IP/extensions/Nuke/Nuke.php" );
require_once( "$IP/extensions/ParserFunctions/ParserFunctions.php" );
require_once( "$IP/extensions/PdfHandler/PdfHandler.php" );
require_once( "$IP/extensions/Poem/Poem.php" );
require_once( "$IP/extensions/Renameuser/Renameuser.php" );
require_once( "$IP/extensions/SimpleAntiSpam/SimpleAntiSpam.php" );
require_once( "$IP/extensions/SpamBlacklist/SpamBlacklist.php" );
require_once( "$IP/extensions/SyntaxHighlight_GeSHi/SyntaxHighlight_GeSHi.php" );
require_once( "$IP/extensions/TitleBlacklist/TitleBlacklist.php" );
require_once( "$IP/extensions/Vector/Vector.php" );
require_once( "$IP/extensions/WikiEditor/WikiEditor.php" );


# End of automatically generated settings.
# Add more configuration options below.

require_once "$IP/extensions/Math/Math.php";
require_once("$IP/extensions/Quiz/Quiz.php");
require_once "$IP/extensions/UserMerge/UserMerge.php";
$wgGroupPermissions['bureaucrat']['usermerge'] = true;
$wgUserMergeProtectedGroups = array();
$wgScriptPath = "/wiki";
$wgArticlePath = "*****";
$wgGroupPermissions['sysop']['interwiki'] = true;
require_once("$IP/extensions/ExpandTemplates/ExpandTemplates.php");
$wgDebugLogFile = "*****";
 $wgFileExtensions[] = 'doc';
 $wgFileExtensions[] = 'PNG';
 $wgFileExtensions[] = 'GIF';
 $wgFileExtensions[] = 'JPG';
 $wgFileExtensions[] = 'JPEG';
 $wgFileExtensions[] = 'bmp';
 $wgFileExtensions[] = 'BMP';
 $wgAllowUserJs = true;
 $wgAllowUserCss = true;
# Enables use of WikiEditor by default but still allow users to disable it in preferences
$wgDefaultUserOptions['usebetatoolbar'] = 1;
$wgDefaultUserOptions['usebetatoolbar-cgd'] = 1;
 
# Displays the Preview and Changes tabs
$wgDefaultUserOptions['wikieditor-preview'] = 1;
 
# Displays the Publish and Cancel buttons on the top right side
$wgDefaultUserOptions['wikieditor-publish'] = 1;
require_once "$IP/extensions/DeleteBatch/DeleteBatch.php";
require_once ( "$IP/extensions/MassEditRegex/MassEditRegex.php" );
$wgGroupPermissions['sysop']['masseditregex'] = true; // Allow administrators to use Special:MassEditRegex
require_once( "$IP/extensions/ReplaceText/ReplaceText.php" );     

#    $wgEnableUploads = true;
    $wgUseTex = true;
    $wgUploadPath = "$wgScriptPath/images";
    $wgUploadDirectory = "$IP/images";
    $wgMathPath = "$wgUploadPath/math";
    $wgMathDirectory = "$wgUploadDirectory/math";
    $wgTmpDirectory = "$wgUploadDirectory/tmp";
    #$wgUploadBaseUrl = false; #not sure about why this one too...
    $wgTexvc = "/usr/bin/texvc"; #install through apt-get instead of make on ./math


    $wgLatexCommand = "/usr/bin/latex"; 
    $wgImageMagickConvertCommand = "/usr/bin/convert";

which *** are private data.

latex.fmt is in wiki/images/tmp.

The error message is rather generic. It doesn't tell us if it failed to save the image, failed to find a executable, etc.

Enable a debug log as explained in Manual:How to debug (I think you already did that with $wgDebugLogFile ) and look for any relevant error. Since the error message may be cached, look at the debug log when previewing an edit that contains math formulas (and maybe try to change one of them), to see if it provides a more detailed error message.