Hi all, Attached is 2nd version of the patch. The improvements are a bit better, although I've removed one change in PolygonSplitterBase which reduces the number of splits in rare cases (e.g. when the map contains large sea areas). I think this change is okay, but it is not related to the LinePreparer and thus should be handled separately. A new binary containing the attached patch(es) is here: http://files.mkgmap.org.uk/download/302/mkgmap.jar If I here no complains I'll commit both patch next wednesday. Gerd ________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Alexandre Loss <alexandre.loss@gmail.com> Gesendet: Samstag, 16. Juli 2016 19:43:23 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] [Patch v1] improve LinePreparer to reduce img size Great discovery Gerd! Enviado do meu iPhone Em 16 de jul de 2016, ?s 14:28, Gerd Petermann <GPetermann_muenchen@hotmail.com<mailto:GPetermann_muenchen@hotmail.com>> escreveu: Hi all, during the last days I tried to find more about the way how mkgmap stores polygons, esp. why we have some limits. While doing that I stumbled over an old comment in LinePreparer.java: // I don't care about getting the smallest possible file size so // err on the side of caution. which made me curious because I do care ;-) I found out that Garmin offers a "trick" in the delta encoding which allows to reduce the needed bytes in some cases, the imgformat-1.0.pdf explains this in detail, search for " only the sign bit is set ". This "trick" helps esp. well when coastline polygons or rivers are stored. I can explain this more detailed if somebody likes to know more, for now I'd like to hear if the trick causes any problems, I did not find any so far. A binary with this and a slightly improved overview_levels_v2.patch can be found here: http://files.mkgmap.org.uk/download/301/mkgmap.jar Depending on the data a single tile with size ~5MB may be reduced by 50 - 500+kB. Gerd <reduceImgSize_v1.patch> _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk<mailto:mkgmap-dev@lists.mkgmap.org.uk> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev