脱密思路：以geojson形式获取postgis的数据，并将geojson数据通过geotools转换为multipolygon,遍历multipolygon中的polygon，并将polygon中的外环点位随机偏移1-5米的范围实现multipolygon数据的脱密
1.遍历multipolygon的polygon，将点位数据偏移后重新生成polygon，并最后返回MultiPolygon
private MultiPolygon multiPolygonDecrypt(MultiPolygon multiPolygon) {
//获取geometry中的坐标 这里用string的方式保存
int geoUnm = multiPolygon.getNumGeometries(); // 一个geometry可能含有n个geometry
Polygon[] polygons = new Polygon[geoUnm];
for (int j = 0; j < geoUnm; j++) {
Polygon singleGeo =(Polygon) multiPolygon.getGeometryN(j); //获取其中每一个geometry
int numGeometries = singleGeo.getNumGeometries();
LinearRing exteriorRing = (LinearRing)singleGeo.getExteriorRing();
int numInteriorRing = singleGeo.getNumInteriorRing();
LinearRing holes[] = new LinearRing[numInteriorRing];
for (int k = 0; k < numInteriorRing; k++) {
LinearRing interiorRing = (LinearRing)singleGeo.getInteriorRingN(k);
holes[k] = interiorRing;
}
//int pointCount = singleGeo.getNumPoints();
Polygon Polygon1 = createPolygon(exteriorRing,holes);
Polygon1.setSRID(4490);
//Coordinate[] coords = singleGeo.getCoordinates();
polygons[j] = Polygon1;
}
// MultiPolygon _multiPolygon = new MultiPolygon(polygons);
GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory( null );
MultiPolygon _multiPolygon = geometryFactory.createMultiPolygon(polygons);
return _multiPolygon;
}
2.shell中的点随机偏移1-5米的范围，并生成新的polygon
public Polygon createPolygon(LinearRing shell,LinearRing holes[]){
Polygon polygon = null;
double random = Math.random();
double brng=360 * random;
double dist=5 * random;
LonLatDecryptUtility llDecryptUt=new LonLatDecryptUtility();
try{
GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory( null );
Coordinate[] shellCoordinates = shell.getCoordinates();
int length = shellCoordinates.length;
int count = 0;
for (Coordinate coordinate : shellCoordinates) {
double x = coordinate.getX();
double y = coordinate.getY();
String[] lonLat = llDecryptUt.computerThatLonLat(x, y, brng, dist).split(",");
x = Double.valueOf(lonLat[0]);
y = Double.valueOf(lonLat[1]);
if(count == length -1){
coordinate.setX(shellCoordinates[0].getX());
coordinate.setY(shellCoordinates[0].getY());
}else{
coordinate.setX(x);
coordinate.setY(y);
}
count++;
}
};
LinearRing ring = geometryFactory.createLinearRing( shellCoordinates );
//LinearRing holes[] = null; // use LinearRing[] to represent holes
polygon = geometryFactory.createPolygon(ring, holes );
}
catch (Exception ex){
System.out.println(ex);
}
return polygon;
}
3. 坐标（经纬度坐标）随机偏移的方法
package com.appleyk.geotools;
public class LonLatDecryptUtility {
/*
* 大地坐标系资料WGS-84 长半径a=6378137 短半径b=6356752.3142 扁率f=1/298.2572236
*/
/** 长半径a=6378137 */
private double a = 6378137;
/** 短半径b=6356752.3142 */
private double b = 6356752.3142;
/** 扁率f=1/298.2572236 */
private double f = 1 / 298.2572236;
/**
* 计算另一点经纬度
*
* @param lon
* 经度
* @param lat
* 维度
* @param lon lat
* 已知点经纬度
* @param brng
* 方位角
* @param dist
* 距离（米）
*/
public String computerThatLonLat(double lon, double lat, double brng, double dist) {
double alpha1 = rad(brng);
double sinAlpha1 = Math.sin(alpha1);
double cosAlpha1 = Math.cos(alpha1);
double tanU1 = (1 - f) * Math.tan(rad(lat));
double cosU1 = 1 / Math.sqrt((1 + tanU1 * tanU1));
double sinU1 = tanU1 * cosU1;
double sigma1 = Math.atan2(tanU1, cosAlpha1);
double sinAlpha = cosU1 * sinAlpha1;
double cosSqAlpha = 1 - sinAlpha * sinAlpha;
double uSq = cosSqAlpha * (a * a - b * b) / (b * b);
double A = 1 + uSq / 16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq)));
double B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq)));
double cos2SigmaM=0;
double sinSigma=0;
double cosSigma=0;
double sigma = dist / (b * A), sigmaP = 2 * Math.PI;
while (Math.abs(sigma - sigmaP) > 1e-12) {
cos2SigmaM = Math.cos(2 * sigma1 + sigma);
sinSigma = Math.sin(sigma);
cosSigma = Math.cos(sigma);
double deltaSigma = B * sinSigma * (cos2SigmaM + B / 4 * (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM)
- B / 6 * cos2SigmaM * (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM * cos2SigmaM)));
sigmaP = sigma;
sigma = dist / (b * A) + deltaSigma;
}
double tmp = sinU1 * sinSigma - cosU1 * cosSigma * cosAlpha1;
double lat2 = Math.atan2(sinU1 * cosSigma + cosU1 * sinSigma * cosAlpha1,
(1 - f) * Math.sqrt(sinAlpha * sinAlpha + tmp * tmp));
double lambda = Math.atan2(sinSigma * sinAlpha1, cosU1 * cosSigma - sinU1 * sinSigma * cosAlpha1);
double C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha));
double L = lambda - (1 - C) * f * sinAlpha
* (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM)));
double revAz = Math.atan2(sinAlpha, -tmp); // final bearing
//System.out.println(revAz);
return (lon+deg(L)+","+deg(lat2));
}
/**
* 度换成弧度
*
* @param d
* 度
* @return 弧度
*/
private double rad(double d) {
return d * Math.PI / 180.0;
}
/**
* 弧度换成度
*
* @param x
* 弧度
* @return 度
*/
private double deg(double x) {
return x * 180 / Math.PI;
}
public static void main(String[] args) {
LonLatDecryptUtility test=new LonLatDecryptUtility();
double lon=121.62486;
double lat=29.87816;
double random = Math.random();
double brng=360 * random;
double dist=5 * random;
String lonLat = test.computerThatLonLat(lon, lat, brng, dist);//121.62487488808823,29.878155097075076
System.out.println(lonLat);
}
}
