[cairo] pdf analysis

Ralph Giles giles at ghostscript.com
Mon Feb 23 16:56:32 PST 2009

On Mon, Feb 23, 2009 at 3:46 PM, Carl Worth <cworth at cworth.org> wrote:

> In the meantime, I'm certainly not aware that cairo is doing anything
> invalid in its PDF creation, nor "stripping" any image information.
> Could you perhaps provide two examples, (one generated with cairo that
> isn't behaving for you, and one without cairo that does what you want),
> of similar PDF documents so that we could look closely at them to see if
> cairo should be doing anything different when it embeds images?

I understood the 'stripping' to be the way cairo generates a PDF
pattern colour space and fills with it, instead of drawing a PDF image
xobject directly on the page. And that Ken's normal preflight tools
aren't smart enough to track the output resolution through this
drawing path. At least, in my tests, cairo embeds image surface
sources as images, but it never does 'q <matrix> cm /x?? Do Q' in a
content stream.

While what cairo does certainly isn't invalid, it's a more natural
expression of cairo's drawing model than pdf's. :)


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