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 -- Frederik Ramm ## eMail [EMAIL PROTECTED] ## N49°00'09" E008°23'33" _______________________________________________ Mapnik-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/mapnik-users
