Re: gEDA-user: pcb printing

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Mon, 2009-03-02 at 12:44 +0000, Kai-Martin Knaak wrote:

> > 1)  is this actually a useful enough feature for people to warrant
> > putting any time into it?  One thing we would probably be able to do
> > better than now is support layer transparency.
> 
> Ack. Transparency when printing is a missing feature.

Sensibly, you want cairo to do this. postscript doesn't support
transparency / compositing like PDF does, so you need fall-backs to
images, or computational geometry to draw each combination of overlapped
layers in the appropriate final colour.

I'm not sure how quickly you'd hit image fall-backs with cairo doing
compositing to a PS backend, but the code required to do otherwise
sounds like it would be a nightmare to write.

As much as I like .ps output in programs, I think we need to skip
straight to .pdf if we want to support translucency in a meaningful way
whilst retaining vector output. IE.. a PDF output HID using shared cairo
code to render.

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)



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