Jon Burgess wrote: > On Sun, 2009-06-21 at 17:00 -0700, Andrew Ayre wrote: >> Jon Burgess wrote: >>> On Sun, 2009-06-21 at 11:28 -0700, Andrew Ayre wrote: >>>> I've given up on trying to compile pgsql2sqlite for now and instead made >>>> some progress on using a georeferenced layer using Gdal. However it >>>> seems that Mapnik is clipping the image even though I have set the map >>>> size to the size of the bitmap and used the bitmap envelope. >>>> >>>> Here are my input files: >>>> >>>> http://files.britishideas.com/public/mapping/osmgeoref.png >>>> http://files.britishideas.com/public/mapping/osmgeoref.pgw >>>> >> [snipped] >>>> And here is the output with the top and bottom of the input PNG missing: >>>> >>>> http://files.britishideas.com/public/mapping/demo.png >>>> >>>> For completeness here is the output XML file: >>>> >>>> http://files.britishideas.com/public/mapping/map.xml >>>> >>>> I used red as a background colour to highlight the issue. Any ideas what >>>> I am doing wrong? I'm sure I'm overlooking something silly. >>> I can not explain it particularly clearly, but I believe the problem is >>> that the original image was not created in latlong projection, hence the >>> 800x361 pixels are not square: >>> >>> $ gdalinfo osmgeoref.png >>> Driver: PNG/Portable Network Graphics >>> Files: osmgeoref.png >>> Size is 800, 391 >>> Coordinate System is `' >>> Origin = (-110.812896694075803,32.220948081346208) >>> Pixel Size = (0.000037724479586,-0.000031870889024) >>> >>> Notice how the pixel sizes are different in the two dimensions. If you >>> adjust the output bitmap to fit this ratio then you get: >>> >>> 800 * 0.000037724479586 / 0.000031870889024 = 947 >>> >>> Then resize the map to this dimension: >>> >>> m = Map(947,391,'+proj=latlong +datum=WGS84') >>> >>> The final output then looks like the original with no clipping. >>> >> Hi Jon, >> >> I tried it and the output isn't quite the same as the input. The top of >> the image now matches but the bottom doesn't. Notice the orange road at >> the very bottom of the input image? It's chopped off the output image. > > No, it looks the same as the input to me. > > There will always be some slight distortion if you are using an image in > a different projection.
Interesting! So with the same input files and same script you get a different output to me. Here is my output: http://files.britishideas.com/public/mapping/output.png Notice how it is the same dimensions as yours but missing quite a bit off the bottom. Also there are lots of jagged lines because it looks like the image has been stretched. I am using Mapnik 0.6.0 on Windows XP. If you are not using Windows perhaps this is a bug in the Windows version? Andy -- Andy PGP Key ID: 0xDC1B5864 _______________________________________________ Mapnik-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/mapnik-users
