Script i made to clean SVG export from Visio (2007). Testing the cleaned SVGs in Chrome, Firefox and Inkscape.

cleanVisioSVG.sh

#! /bin/sh

#set px for font size with metric 
perl -pi -e 's/font-size:(\d+);/font-size:$1px;/g'  "$1"
#replace em metrics with px  (this is a bit brittle, as the ems are relative to the container text)

#First the @dy=".." (multiply by 8)
perl  -pi -e 's/dy=\"(\d+(\.\d+)?)em\"/"dy=\"".sprintf("%.1f",$1*8)."px\""/ge' "$1"
#Then all the others (multiply by 12, which is the default font size set bu visio export)
perl  -pi -e 's/(\d+(\.\d+)?)em/sprintf("%.1f",$1*12)."px"/ge' "$1"

#Convert in to cm (European ;)
perl  -pi -e 's/(\d+(\.\d+)?)in/sprintf("%.1f",$1*2.54)."cm"/eg' "$1"


#Remove comments (just cleanup)
xmlstarlet ed -L -d "//comment()" "$1"
#Remove all nodes from Visio namespace 
xmlstarlet ed -L -d "//node()[namespace-uri()='http://schemas.microsoft.com/visio/2003/SVGExtensions/']" "$1"
#Remove all attributes from Visio namespace 
xmlstarlet ed -L -d "//attribute::*[namespace-uri()='http://schemas.microsoft.com/visio/2003/SVGExtensions/']" "$1"
#Remove title and desc elements (just cleanup)
xmlstarlet ed -L -d "//node()[local-name()='title']" "$1"
xmlstarlet ed -L -d "//node()[local-name()='desc']" "$1"
#remove visio namespace declaration
perl -pi -e 's/xmlns:v=".*?"//' "$1"

#remove blank lines
sed -i '/^\s*$/d'  "$1"