[reportlab-users] PDF Transparency

King Simon-NFHD78 simon.king at motorola.com
Thu Nov 27 13:09:37 EST 2008

> -----Original Message-----

> From: reportlab-users-bounces at reportlab.com

> [mailto:reportlab-users-bounces at reportlab.com] On Behalf Of

> Robin Becker

> Sent: 27 November 2008 17:46

> To: Support list for users of Reportlab software

> Subject: Re: [reportlab-users] PDF Transparency


> King Simon-NFHD78 wrote:

> > Hi,

> >

> > Does anyone have any plans to support the PDF Transparency model in

> > ReportLab?

> ..........

> >

> > I can post the patch if anyone is interested.

> >

> > Thanks for listening,

> >

> > Simon King

> .......

> by all means post the patch. I guess the main problem is that

> we'd probably like

> to expose 1.4 capabilities in a controlled way. Perhaps we

> should have an

> attribute that specified which level of PDF is being aimed

> at. I guess that

> should probably be on the PDFDoc, but perhaps it should be

> settable on the

> canvas (as that needs support as well).

> --

> Robin Becker

OK, here's the patch - it's a little ugly at the moment.

I was thinking a little more about managing the ExtGState dictionaries.
Do you think it is reasonable to create a state for each 'extended
attribute' value? For example, setting both the stroke alpha and fill
alpha results in the creation of two states. This keeps the canvas
interface nice and simple, possibly at the expense of efficiency.

I suppose you could expose add_extgstate method and activate_extgstate
as well, for users who want to manage them manually.

Thanks again,

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