[cairo] Writing Surface to PNG based on Window Context: POSSIBLE?
darethehair at gmail.com
Sat Mar 21 17:01:19 PDT 2009
Neil Mayhew wrote:
> On 2009-03-21 07:20, darethehair wrote:
>> Gerdus van Zyl wrote:
>>> tsurf = ctx.get_target()
> Oops! Sorry, I forgot about that option. I am a newbie too.
>> I couldn't help thinking that there must be some better/easier way of
>> somehow transferring one to another, without the hassle of repeating
>> the same drawing code all over again.
> True, but there are limitations of rendering it to an on-screen window
> and then sucking the pixels back from the screen to a file. For example,
> on some systems, if the window is partially obscured you may not get all
> the pixels back again. Also, you are limited to the resolution and
> imaging model of the screen. So I don't think you'd be able to preserve
> transparency in the original PNG (eg if your moon image has a
> transparent background). Finally, you only have the option of
> image-based rendering. With my approach, you can optionally render to an
> SVG or PDF, so that your circles etc. come out sharp at any level of
> magnification. That may not be important for your current application,
> but it would be in the general case.
> BTW, if all you need to do is add lines, circles and text to images in a
> batch-oriented way, you could also look at ImageMagick, which has
> various command-line tools for doing that, and doesn't require any
> programming. But it's not as much fun as cairo! :-)
Neil, I agree with you 100%. After successfully doing the 'easy' PNG
screenshot, I realized that SVG/PDF was not going to be so easy :) For
now, the easy-peazy PNG thing is good enough, but if I ever do attempt
to extend this to vector-graphics, then I will have to take the long
road approach. Yes, I also love ImageMagick, and I do use it for my
'batch/command-line' image processing.
I actually feel a bit weird and guilty when I find out that the 'back
end' graphics engine of some of my favourite apps use Cairo -- as if it
is a secret that mere mortals like myself shouldn't know and use in my
own apps! I am so glad that Maemo (the OS of the Nokia Internet Tablet
devices) uses Python and PyGTK and PyGame and PyCairo so that I can
pretend that I am a professional developer too! :)
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