我有一个光栅图像(Tiff 格式)和一个转换为数组的 shapefile 格式的多边形区域。我希望找到一种优雅的方法来创建一个数组,其中多边形边界内的所有元素都有 1 值,多边形外的所有元素都有值 0。我的最终目标是用从 shapefile 派生的数组屏蔽从图像派生的数组.
我有以下问题,感谢您的帮助:
在使用np.zeros((ds.RasterYSize, ds.RasterXSize))和我的多边形边界的地理空间坐标的像素位置创建一个空数组后,用 1 填充数组内的多边形的最佳解决方案是什么?
from osgeo import gdal, gdalnumeric, ogr, osr
import osgeo.gdal
import math
import numpy
import numpy as np
def world2Pixel(geoMatrix, x, y):
"""
Uses a gdal geomatrix (gdal.GetGeoTransform()) to calculate
the pixel location of a geospatial coordinate
(source http://www2.geog.ucl.ac.uk/~plewis/geogg122/vectorMask.html)
geoMatrix
[0] = top left x (x Origin)
[1] = w-e pixel resolution (pixel Width)
[2] = rotation, 0 if image is "north up"
[3] = top left y (y Origin)
[4] = rotation, 0 if image is "north up"
[5] = n-s pixel resolution (pixel Height)
"""
ulX = geoMatrix[0]
ulY = geoMatrix[3]
xDist = geoMatrix[1]
yDist = geoMatrix[5]
rtnX = geoMatrix[2]
rtnY = geoMatrix[4]
pixel = np.round((x - ulX) / xDist).astype(np.int)
line = np.round((ulY - y) / xDist).astype(np.int)
return (pixel, line)
# Open the image as a read only image
ds = osgeo.gdal.Open(inFile,gdal.GA_ReadOnly)
# Get image georeferencing information.
geoMatrix = ds.GetGeoTransform()
ulX = geoMatrix[0] # top left x (x Origin)
ulY = geoMatrix[3] # top left y (y Origin)
xDist = geoMatrix[1] # w-e pixel resolution (pixel Width)
yDist = geoMatrix[5] # n-s pixel resolution (pixel Height)
rtnX = geoMatrix[2] # rotation, 0 if image is "north up"
rtnY = geoMatrix[4] #rotation, 0 if image is "north up"
# open shapefile (= border of are of interest)
shp = osgeo.ogr.Open(poly)
source_shp = ogr.GetDriverByName("Memory").CopyDataSource(shp, "")
# get the coordinates of the points from the boundary of the shapefile
source_layer = source_shp.GetLayer(0)
feature = source_layer.GetNextFeature()
geometry = feature.GetGeometryRef()
pts = geometry.GetGeometryRef(0)
points = []
for p in range(pts.GetPointCount()):
points.append((pts.GetX(p), pts.GetY(p)))
pnts = np.array(points).transpose()
print pnts
pnts
array([[ 558470.28969598, 559495.31976318, 559548.50931402,
559362.85560495, 559493.99688721, 558958.22572622,
558529.58862305, 558575.0174293 , 558470.28969598],
[ 6362598.63707171, 6362629.15167236, 6362295.16466266,
6362022.63453845, 6361763.96246338, 6361635.8559779 ,
6361707.07684326, 6362279.69352024, 6362598.63707171]])
# calculate the pixel location of a geospatial coordinate (= define the border of my polygon)
pixels, line = world2Pixel(geoMatrix,pnts[0],pnts[1])
pixels
array([17963, 20013, 20119, 19748, 20010, 18939, 18081, 18172, 17963])
line
array([35796, 35734, 36402, 36948, 37465, 37721, 37579, 36433, 35796])
#create an empty array with value zero using
data = np.zeros((ds.RasterYSize, ds.RasterXSize))