Re: Creating CGFont from PDF Tf operator
Re: Creating CGFont from PDF Tf operator
- Subject: Re: Creating CGFont from PDF Tf operator
- From: Marcel Weiher <email@hidden>
- Date: Wed, 28 Aug 2013 14:22:13 +0200
On Aug 27, 2013, at 14:46 , Graham Cox <email@hidden> wrote:
> Parsing a PDF, I need to handle the Tf (set font) operator. The font situation in PDF files is inordinately complicated, and reading the spec alone is not really leading to the light-bulb moment.
Yes, there are many dark tunnels ahead...
> Basically, when I get the Tf operator, I need to end up with a CGFontRef I can use. I see a number of CGFontCreate… methods, none of which really fit anything I can see in the PDF spec itself. Perhaps CGFontCreateWithDataProvider is the "magic bullet" that just works behind the scenes to make sense of the almost innumerable PDF variations, but I can't see how I even get to the point where I could use it.
Well, first you have a /Font. This should contain a reference to a /FontDescriptor. If the font is embedded in the file, then you have a /FontFile reference ( or /FontFile1, /FontFile2, /FontFile3), which then points to the PDF Stream containing the actual font.
If there is no /FontFile, the font is not embedded and you need to figure out where to get the font to use (by name) or supply a fallback font, which has to match the encoding and metrics.
> 2013-08-27 12:08:10.304 PDFParser[43098:303] 'Subtype'=[Name]'Type0',
> 2013-08-27 12:08:10.304 PDFParser[43098:303] 'ToUnicode'=[Stream],
>
> I see this in the PDF spec; it's just one among many possible font types and formats, but I have no idea how to go from this to a CGFontRef.
Ahh, a Type0 font. Those are fun!
Cheers,
Marcel
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