Re: [Devel] how to cope with bitmap glyphs?

[George Williams]

On Thu, 2004-04-08 at 19:39, 沈 狼 wrote:

>  from the scratch,  for a give word, now I wannt to know how to render it.
> 
> so far, I know in the true type font  there is a cmap for us to lookup the 
> glyphid corresponding to the word I want to render. so what's the usage of 
> the bitmap if the EBDT,EBLC tables exist? someone has suggest me to read 
> GDEF ,GSUB, GPOS table, 
No, I said they could be related to bitmaps, (ie. to handle the font
properly you should process those table no matter what format your
glyphs are in). They don't help you get bitmaps connected to glyphs.
> but I dont yet know the relation between the bitmap 
> & glyphid. would you give me a exaborative
You do realize that freetype will do this translation for you if you
want to use it...

But if you want code snippets...
look at src/sfnt/ttsbit.c in the freetype distribution, or
http://cvs.sourceforge.net/viewcvs.py/*checkout*/fontforge/fontforge/fontforge/parsettfbmf.c?content-type=text%2Fplain&rev=1.2
both can read the EBDT/EBLC table.

Essentially, the EBLC contains several lookup tables.
First there are a series of pixel sizes described.
Each pixel size points to a (complicated) list of glyphs ranges with
pointers into the EBDT table.

It is fairly well described in the opentype spec
  http://partners.adobe.com/asn/tech/type/opentype/eblc.jsp
  http://partners.adobe.com/asn/tech/type/opentype/ebdt.jsp