Hi,
I am starting to use mapnik with python and I have two questions:
1. Is there any datasource for mysql?
2. Does exist a way to implement a datasource from python?
Thanks
El sáb, 14-06-2008 a las 02:25 +0200, Frederik Ramm escribió:
> Hi,
>
> > > Fred, Image32 does appear to be a pretty basic type
> > > (yes it's a mapnik class). If you're using C++ at all (or have
> > > the option to) I'd highly suggest you take a look at CImg...
> >
> > I'm using C++ and tend to stick what I already know (which is
> > GD and ImageMagick) but will check out CImg as well.
>
> Ok here's an update on what I've achieved so far.
>
> I have successfully used the cairo_renderer to draw onto a cairo surface
> which I subsequently rendered onto a new surface with scaling applied.
> This gives the desired result, with good quality, but unfortunately it
> is very slow (full execution time for rendering a 2° by 2° OSM styled
> map onto an 800x600 canvas - 15 seconds with cairo compared to 7 seconds
> with AGG).
>
> Actually applying the scaling to the cairo context used internally by
> the cairo_renderer, instead of scaling the resulting surface like I do,
> gains you a second but still the performance makes this unsuitable for
> my task.
>
> So I went back to the idea of using the original AGG render result and
> somehow scale that bitmap before returning it. Unfortunately, neither GD
> nor ImageMagick nor CImg have a convenient method to work with the kind
> of interleaved data store that backs the Image32 type (GD stores an
> array of interleaved three-byte pixels and the alpha value is elsewhere;
> ImageMagick has 64bit pixels; CImg uses a non-interlaved four byte
> store, while Image32 is an interleaved four byte store). Somewhat
> exasperated, I did the ugliest thing and had Mapnik write the image to
> disk for me, then called ImageMagick externally to scale the PNG file,
> then read it back in - which adds an extra half second to processing but
> at least works for testing.
>
> Since I don't need top-notch image quality for this corner case where
> the WMS client requests non-matching width/height, I will perhaps try
> the homebrew way of simply duplicating or dropping full lines in the PNG
> output to achieve the desired height. I have to roll my own PNG output
> from Image32 anyway because (unlike cairo which supports callback
> output) the existing Mapnik code will only create PNG files on disk and
> not in memory, where I need them if I want to return them to the user.
>
> If anyone in the know reads this and has some insight to share, do speak up.
>
> Bye
> Frederik
>
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