利用Geotools来转换影像的坐标系[转]
使用Operations类下的resample方法(重采样)可以解决这个问题，它的方法定义如下：
Coverage org.geotools.coverage.processing.Operations.resample(Coverage source, CoordinateReferenceSystem crs) throws CoverageProcessingException
File file = new File("xxxx.tif");
if(file.exists()){
Reader br = new Reader();
GridCoverage2D old2D = br.getGridCoverage2D(file);
final CoordinateReferenceSystem WGS = CRS.decode("EPSG:3857");
final CoordinateReferenceSystem sourceCRS = old2D.getCoordinateReferenceSystem();
System.out.println(String.format("源坐标系为: %s", sourceCRS.getName()));
GridCoverage2D new2D = (GridCoverage2D) Operations.DEFAULT.resample(old2D, WGS);
System.err.println(String.format("目标坐标系为: %s", new2D.getCoordinateReferenceSystem().getName()))；
}
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作者：WilsonOnIsland
来源：CSDN
原文：https://blog.csdn.net/u013323965/article/details/79453383
1.计算指定像素坐标点的坡度
public float calcSlope(int cellX, int cellY, PlanarImage image) throws IOException {
DecimalFormat df = new DecimalFormat("#.0000");
final int[] dest = null;
int e = image.getTile(image.XToTileX(cellX), image.YToTileY(cellY)).getPixel(cellX, cellY, dest)[0];
int e1 = image.getTile(image.XToTileX(cellX - 1), image.YToTileY(cellY)).getPixel(cellX - 1, cellY, dest)[0];
int e2 = image.getTile(image.XToTileX(cellX), image.YToTileY(cellY - 1)).getPixel(cellX, cellY - 1, dest)[0];
int e3 = image.getTile(image.XToTileX(cellX + 1), image.YToTileY(cellY)).getPixel(cellX + 1, cellY, dest)[0];
int e4 = image.getTile(image.XToTileX(cellX), image.YToTileY(cellY + 1)).getPixel(cellX, cellY + 1, dest)[0];
int e5 = image.getTile(image.XToTileX(cellX - 1), image.YToTileY(cellY - 1)).getPixel(cellX - 1, cellY - 1,
dest)[0];
int e6 = image.getTile(image.XToTileX(cellX + 1), image.YToTileY(cellY - 1)).getPixel(cellX + 1, cellY - 1,
dest)[0];
int e7 = image.getTile(image.XToTileX(cellX + 1), image.YToTileY(cellY + 1)).getPixel(cellX + 1, cellY + 1,
dest)[0];
int e8 = image.getTile(image.XToTileX(cellX - 1), image.YToTileY(cellY + 1)).getPixel(cellX - 1, cellY + 1,
dest)[0];
double slopeWE = ((e8 + 2 * e1 + e5) - (e7 + 2 * e3 + e6)) / (8 * 2041.823085);// 东西方向坡度
double slopeNW = ((e7 + 2 * e4 + e8) - (e6 + 2 * e2 + e5)) / (8 * 2041.823085);// 南北方向坡度
double slope = 100*(Math.sqrt(Math.pow(slopeWE, 2) + Math.pow(slopeNW, 2)));
return Float.parseFloat(df.format(slope));
}2.DEM数据测试用例
@Test
public void testCalcSlope() throws NoSuchAuthorityCodeException, FactoryException, IOException {
String path = "D:\\workData\\geotiff\\testTiff.tif";
String outputPath = "D:\\workData\\geotiff\\output.tif";
File file = new File(path);
// 设置tiff影像默认设置
Hints tiffHints = new Hints();
tiffHints.add(new Hints(Hints.FORCE_LONGITUDE_FIRST_AXIS_ORDER, Boolean.TRUE));
// 默认坐标系EPSG:3857
// tiffHints.add(new Hints(Hints.DEFAULT_COORDINATE_REFERENCE_SYSTEM, CRS.decode("EPSG:4326")));
tiffHints.add(new Hints(Hints.DEFAULT_COORDINATE_REFERENCE_SYSTEM, DefaultGeographicCRS.WGS84));
GeoTiffReader reader = new GeoTiffReader(file, tiffHints);
GridCoverage2D coverage = reader.read(null);
Envelope env = coverage.getEnvelope();
PlanarImage image = (PlanarImage) coverage.getRenderedImage();
int width = image.getWidth(); // Image Width
int height = image.getHeight(); // Image Height
// 计算每个栅格的坡度
float[][] slopeData = new float[height][width];
for (int i = 1; i < height + 1; i++) {
for (int j = 1; j < width + 1; j++) {
float slope = SlopeUtil.INSTANCE.calcSlope(j, i, image);
slopeData[i - 1][j - 1] = slope;
}
}
GridCoverageFactory factory = new GridCoverageFactory();
GridCoverage2D outputCoverage = factory.create("test", slopeData, env);
GeoTiffWriter writer = new GeoTiffWriter(new File(outputPath));
writer.write(outputCoverage, null);
writer.dispose();
}
功能需求：给定同一区域不同时间的无人机影像数据，求出区域内影像变化部分，并矢量化成GeoJSON返回给前端。
1.将两幅图像进行相减与二值化操作
public GridCoverage2D tiffSubtract(String sourceTiffPath, String targetTiffPath, float diffLimit)
throws IOException {
File sourceTiff = new File(sourceTiffPath);
File targetTiff = new File(targetTiffPath);
if (!sourceTiff.exists() || !targetTiff.exists()) {
throw new FileNotFoundException(sourceTiffPath + " or " + targetTiffPath + " do not exist!");
}
// 中间数据tiff存储路径
String tempTiff = sourceTiff.getParent() + File.separator + "output.tiff";
// tiff文件坐标系设置
Hints tiffHints = new Hints();
tiffHints.add(new Hints(Hints.FORCE_LONGITUDE_FIRST_AXIS_ORDER, Boolean.TRUE));
tiffHints.add(new Hints(Hints.DEFAULT_COORDINATE_REFERENCE_SYSTEM, DefaultGeographicCRS.WGS84));
GeoTiffReader sourceReader = new GeoTiffReader(sourceTiff, tiffHints);
GeoTiffReader targetReader = new GeoTiffReader(targetTiff, tiffHints);
GridCoverage2D sourceCoverage = sourceReader.read(null);
GridCoverage2D targetCoverage = targetReader.read(null);
RenderedImage sourceImage = sourceCoverage.getRenderableImage(0, 1).createDefaultRendering();
RenderedImage targetImage = targetCoverage.getRenderableImage(0, 1).createDefaultRendering();
Raster sourceRaster = sourceImage.getData();
Raster targetRaster = targetImage.getData();
int width = sourceRaster.getWidth();
int height = sourceRaster.getHeight();
// System.out.println("pixels : width:" + width + ";height:" + height);
Envelope2D sourceEnv = sourceCoverage.getEnvelope2D();
float[][] difference = new float[height][width];
float s;
float t;
// 修改算法,提取差异值大于阈值的部分
// 将图像二值化
for (int x = 0; x < width - 1; x++) {
for (int y = 0; y < height - 1; y++) {
// System.out.println("x:" + x + ";y:" + y);
s = sourceRaster.getSampleFloat(x, y, 1);
t = targetRaster.getSampleFloat(x, y, 1);
float diff = t - s;
if (diff > diffLimit) {
difference[y][x] = 100f;
} else {
difference[y][x] = 0f;
}
}
}
GridCoverageFactory factory = new GridCoverageFactory();
GridCoverage2D outputCoverage = factory.create("subtractTiff", difference, sourceEnv);
GeoTiffWriter writer = new GeoTiffWriter(new File(tempTiff));
writer.write(outputCoverage, null);
writer.dispose();
return outputCoverage;
}
2.调用geoTools的PolygonExtractionProcess将图像相减操作结果进行矢量化
public String polygonExtraction(GridCoverage2D tiffCoverage, String shpPath)
throws MismatchedDimensionException, IndexOutOfBoundsException, NoSuchAuthorityCodeException,
ParseException, FactoryException, TransformException, SchemaException, IOException {
PolygonExtractionProcess process = new PolygonExtractionProcess();
SimpleFeatureCollection features = process.execute(tiffCoverage, 0, Boolean.TRUE, null, null, null, null);
features = this.polygonPostprocess(features, 10d);
SimpleFeatureType type = features.getSchema();
// ShapeFileWriter.INSTANCE.write(shpPath, features, type);
this.toGeoJSON(features);
return shpPath;
}
3.对矢量化后的多边形对象进行过滤，删除面积过小的细碎多边形
private SimpleFeatureCollection polygonPostprocess(SimpleFeatureCollection features, double aeraLimit)
throws IndexOutOfBoundsException, ParseException, NoSuchAuthorityCodeException, FactoryException,
MismatchedDimensionException, TransformException, SchemaException {
//坐标转换,从4326转成3857
CoordinateReferenceSystem dataCRS = DefaultGeographicCRS.WGS84;
CoordinateReferenceSystem targerCRS = CRS.decode("EPSG:3857");
boolean lenient = true; // allow for some error due to different datums
MathTransform transform = CRS.findMathTransform(dataCRS, targerCRS, lenient);
final SimpleFeatureType TYPE = DataUtilities.createType("Location",
"the_geom:Polygon:srid=3857,DN:String,Aera:Double");
List<SimpleFeature> projectedFeatureList = new ArrayList<SimpleFeature>();
GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();
WKTReader reader = new WKTReader(geometryFactory);
SimpleFeatureBuilder builder = new SimpleFeatureBuilder(TYPE);
SimpleFeatureIterator iterator = features.features();
try {
while (iterator.hasNext()) {
SimpleFeature feature = iterator.next();
Polygon polygon = (Polygon) feature.getDefaultGeometry();
polygon = (Polygon) JTS.transform(polygon, transform);
double aera = polygon.getArea();
// 多边形面积大于阈值
if (aera >= aeraLimit) {
builder.add(polygon);
builder.add(feature.getAttribute(1).toString());
builder.add(aera);
SimpleFeature tempFeature = builder.buildFeature(null);
projectedFeatureList.add(tempFeature);
}
}
} finally {
iterator.close();
}
System.out.println(projectedFeatureList.size());
return new ListFeatureCollection(TYPE, projectedFeatureList);
}
4.将最终结果以GeoJSON格式返回
private void toGeoJSON(SimpleFeatureCollection featureCollection) {
SimpleFeatureIterator it = featureCollection.features();
GeoJsonWriter geoJsonWriter = new GeoJsonWriter();
while(it.hasNext()) {
SimpleFeature tempFeature = it.next();
Geometry geometry = (Geometry) tempFeature.getDefaultGeometry();
String json = geoJsonWriter.write(geometry);
System.out.println(json);
}
}
作者：z362831561
链接：https://www.jianshu.com/p/6b7addbe8739
来源：简书
