问题
I have a KML file with placemarkers, each of which has polygon coordinates. I'd like to change the fill color of the polygons on the fly, depending on values I read in from a json file. My understanding is that Google caches kml files, so you can't easily change the fill color of polygons on the fly.
So I'm trying to convert my kml polygons into svg paths so that I can use Raphael to place my polygons on my Google map. Then I can change fill colors with javascript.
But how do I convert polygon coordinates to svg paths, does anyone know?
A sample set of coordinates would be:
<Polygon><outerBoundaryIs><LinearRing><coordinates>-80.098181,40.42127 -80.096479,40.421262 -80.096464,40.421409 -80.096448,40.421551 -80.096444,40.421583 -80.096434,40.421666 -80.096406,40.421931 -80.096389,40.422087 -80.096353,40.422423 -80.09583,40.426101 -80.095525,40.428234 -80.095315,40.429714 -80.095276,40.429989 -80.092585,40.428593 -80.092273,40.428431 -80.09069,40.430519 -80.090384,40.430924 -80.08989,40.430618 -80.089699,40.4305 -80.089499,40.430359 -80.088738,40.429886 -80.088418,40.429688 -80.088254,40.429585 -80.087931,40.429384 -80.087086,40.428859 -80.086867,40.428722 -80.086658,40.428592 -80.086493,40.42849 -80.08617,40.428282 -80.086177,40.428265 -80.08621,40.428188 -80.0864,40.427742 -80.086397,40.42749 -80.086394,40.427125 -80.08631,40.426427 -80.086335,40.425887 -80.086235,40.425409 -80.085776,40.425327 -80.085442,40.42527 -80.084993,40.424585 -80.085076,40.42448 -80.085542,40.423842 -80.085679,40.423125 -80.085659,40.423011 -80.085626,40.422827 -80.085191,40.421758 -80.08467,40.420859 -80.084258,40.420336 -80.083828,40.4201 -80.083078,40.420005 -80.082504,40.420072 -80.081444,40.420196 -80.080888,40.420181 -80.080775,40.420178 -80.080604,40.420173 -80.080122,40.420161 -80.079753,40.420151 -80.07947,40.420144 -80.079287,40.420139 -80.078239,40.420296 -80.077661,40.420418 -80.076213,40.420726 -80.075673,40.420766 -80.075298,40.420719 -80.075127,40.420625 -80.074909,40.420307 -80.075028,40.419779 -80.07539,40.419028 -80.07583,40.41836 -80.076065,40.418108 -80.076528,40.417616 -80.077217,40.417124 -80.077503,40.417002 -80.077725,40.416907 -80.078391,40.416622 -80.078614,40.416528 -80.078657,40.41651 -80.078693,40.416491 -80.078755,40.416457 -80.079174,40.416233 -80.079205,40.416217 -80.079292,40.416128 -80.079439,40.415977 -80.079456,40.41596 -80.079614,40.415473 -80.079604,40.415377 -80.079584,40.415179 -80.07958,40.415168 -80.079539,40.415042 -80.079499,40.414915 -80.079407,40.414785 -80.079742,40.414965 -80.08086,40.415568 -80.081458,40.415889 -80.081535,40.41593 -80.082292,40.416343 -80.08238,40.416392 -80.082597,40.41651 -80.082624,40.416525 -80.082787,40.416614 -80.083508,40.417007 -80.083934,40.417239 -80.084422,40.417505 -80.084622,40.417432 -80.084852,40.417348 -80.085329,40.417179 -80.085419,40.417141 -80.085948,40.41695 -80.086252,40.417184 -80.088463,40.418885 -80.088964,40.418631 -80.089036,40.418595 -80.089145,40.418539 -80.089173,40.418525 -80.089346,40.418438 -80.089376,40.418457 -80.089398,40.418471 -80.089964,40.418827 -80.090299,40.419055 -80.091306,40.419739 -80.091642,40.419967 -80.091803,40.420088 -80.091966,40.420043 -80.092445,40.419915 -80.092561,40.419885 -80.096792,40.418748 -80.098853,40.41815 -80.098868,40.418242 -80.09943,40.421273 -80.098181,40.42127</coordinates></LinearRing></outerBoundaryIs></Polygon>
回答1:
Disclaimer: I'm a bit rusty on geodetics, but think your #1 problem here is the coordinate system - lat, lng are projection-dependent data points, whereas your screen is a flat pixel one. What you need to do is convert these to northing and easting points first.
There is a projection conversion library out there called proj.4 - use this to convert your coordinates. If needed, there is a javascript port of it that you can easily adapt for your use at https://trac.osgeo.org/proj/
Generic conversion process would go like this (LAT, LNG are actual coordinates.)
var source = new Proj4js.Proj('WGS84');
var dest = new Proj4js.Proj('GOOGLE');
var p = new Proj4js.Point( LATITUDE, LONGITUDE ); // replace with actual coords!
var pdest = Proj4js.transform(source, dest, p);
At this point, pdest.x and pdest.y will contain your SVG-compatible coordinates.
After your coordinates are converted to pixel units, simply plot them - and mind the range and units. Northing and easting coordinates will be in 800,000 range, so you will likely be applying some transformations, such as translation and scaling.
End result should look like this (being rusty, I may have messed up and flipped lat/lng around, etc.)
Here's a working jsfiddle with a conversion and plot: http://jsfiddle.net/LPzKV/1/
来源：https://stackoverflow.com/questions/13460415/convert-kml-polygons-to-svg-paths