[WWcvs] webwork-modperl: Change arguments passed to dvipng

[Arnie P. v. a. <we...@ma...>]

Log Message:
-----------
Change arguments passed to dvipng

Modified Files:
--------------
    webwork-modperl/lib/WeBWorK:
        Constants.pm

Revision Data
-------------
Index: Constants.pm
===================================================================
RCS file: /webwork/cvs/system/webwork-modperl/lib/WeBWorK/Constants.pm,v
retrieving revision 1.29
retrieving revision 1.30
diff -Llib/WeBWorK/Constants.pm -Llib/WeBWorK/Constants.pm -u -r1.29 -r1.30
--- lib/WeBWorK/Constants.pm
+++ lib/WeBWorK/Constants.pm
@@ -75,12 +75,19 @@
 
 # Arguments to pass to dvipng. This is dependant on the version of dvipng.
 # 
-# For dvipng < 1.0
+# For dvipng versions 0.x
 #     $WeBWorK::PG::ImageGenerator::DvipngArgs = "-x4000.5 -bgTransparent -Q6 -mode toshiba -D180";
-# For dvipng >= 1.0
+# For dvipng versions 1.0 to 1.5
 #     $WeBWorK::PG::ImageGenerator::DvipngArgs = "-bgTransparent -D120 -q -depth";
 # 
-$WeBWorK::PG::ImageGenerator::DvipngArgs = "-bgTransparent -D120 -q -depth";
+# For dvipng versions 1.6 (and probably above)
+#     $WeBWorK::PG::ImageGenerator::DvipngArgs = "-bgtransparent -D120 -q -depth";
+# Note: In 1.6 and later, bgTransparent gives alpha-channel transparency while 
+# bgtransparent gives single-bit transparency. If you use alpha-channel transparency,
+# the images will not be viewable with MSIE.  bgtransparent works for versions lower
+# than 1.6, but does not give transparent backgrounds.
+#
+$WeBWorK::PG::ImageGenerator::DvipngArgs = "-bgtransparent -D120 -q -depth";
 
 # If true, don't delete temporary files
 #