[#3566] doxygen: changed png to svg

Author: tomaszmrugalski

doc/devel/Doxyfile

@@ -1766,7 +1766,7 @@ OBFUSCATE_EMAILS       = YES
 # The default value is: png.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-HTML_FORMULA_FORMAT    = png
+HTML_FORMULA_FORMAT    = svg
 
 # Use this tag to change the font size of LaTeX formulas included as images in
 # the HTML documentation. When you change the font size after a successful
@@ -2723,7 +2723,7 @@ DIR_GRAPH_MAX_DEPTH    = 1
 # The default value is: png.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-DOT_IMAGE_FORMAT       = png
+DOT_IMAGE_FORMAT       = svg
 
 # If DOT_IMAGE_FORMAT is set to svg, then this option can be set to YES to
 # enable generation of interactive SVG images that allow zooming and panning.