OGC Public Forum :

[ahall]

Hi

I wonder how the MarkIndex work (in PointSymbolizer/Graphic/Mark). What exatly is it and how can I find out the MarkIndexes of the glyphs in a truetype font-file?

I searched the internet very thoroughly but can´t find any examples where the MarkIndex have been used. I also looked through the SE specification but it doesn´t say very much about this topic.

I also wonder how the format-element will look when using a truetype font-file.

Thanks for help.

[creed]

I will pass your question onto the OGC SLD/SE community.

Regards
_________________
Carl Reed, PhD

[creed]

Here is a detailed answer from an SLD guru from CubeWerx:

> I wonder how the MarkIndex work (in PointSymbolizer/Graphic/Mark). What
> exatly is it and how can I find out the MarkIndexes of the glyphs in
> a truetype font-file?

SE is under-specified on what to do with a TrueType font. Its mechanism
is intended to be generic, but there is a practical problem when dealing
with TrueType fonts as to whether the raw glyph index is intended or
the Unicode character code point that the glyph represents. Strictly,
I'd assume it's supposed to be the raw glyph index, though Uncode code
points are more convenient to deal with.

For example, in the following set of TrueType symbols for Emergency
Response Symbology:

http://www.mirrorservice.org/sites/www.ibiblio.org/gentoo/distfiles/ers_v220.zip

in the embedded file
"ersSymbolsVersion0202/ersV2sym/ERS_v2_Operations_S4_sym.ttf", the symbol
for a disabled ambulance service is glyph index 256 (0x100) and Unicode
character 'C' U+0043 (67 decimal). So, I'd say that you would use
<MarkIndex> 256. In the newer version of the symbols, in the embedded
file "ersSymbolsVersion0202/ersV2txt/ERS_v2_Operations_S4_txt.ttf", the
symbol is at raw glyph index 67 (0x43), which happily coincides with the
Unicode character 'C'.

You may need to use a font editor to see what the raw glyph indexes inside
a TrueType file are. I used open-source FontForge to look at the ERS one.

> I also wonder how the format-element will look when using a truetype
> font-file.

According to the following message, there is no official MIME type for
TrueType:

http://mx.gw.com/pipermail/file/2009/000400.html

However, the most common MIME type used is "application/x-font-ttf".

Hope this helps.

Regards
_________________
Carl Reed, PhD