render in high dpi and resample

mathtex.c

@@ -325,7 +325,7 @@ static	char *sizedirectives[] = { NULL, /* fontsize directives */
  * dpi/density info for dvipng/convert
  * ----------------------------------- */
 #if !defined(DPI)
-  #define DPI "120"
+  #define DPI "600"
 #endif
 static	char density[256] = DPI;	/*-D/-density arg for dvipng/convert*/
 /* ---
@@ -1537,7 +1537,7 @@ char  errormsg[1024] =			/* latex runs but can't make .dvi */
 	"\\atop \\mbox{an error in your expression.}$}";
 char  usepackage[1024] = "\000";	/* additional \usepackage{}'s */
 char  convertargs[1024] =		/* args/switches for convert */
-	" -density %%dpi%% -gamma %%gamma%%"
+	" -density %%dpi%% -resample 120 -gamma %%gamma%%"
 	/*" -border 0% -fuzz 2%"*/
 	" -trim -transparent \"#FFFFFF\" ";
 char  dvipngargs[1024] =		/* args/switches for dvipng */