在Python中用GDAL实现矢量对栅格的切割实例


Posted in Python onMarch 11, 2020

概述:

本文讲述如何在Python中用GDAL实现根据输入矢量边界对栅格数据的裁剪。

效果:

在Python中用GDAL实现矢量对栅格的切割实例

裁剪前

在Python中用GDAL实现矢量对栅格的切割实例

矢量边界

在Python中用GDAL实现矢量对栅格的切割实例

裁剪后

实现代码:

# -*- coding: utf-8 -*-
"""
@author lzugis
@date 2017-06-02
@brief 利用shp裁剪影像
"""
 
from osgeo import gdal, gdalnumeric, ogr
from PIL import Image, ImageDraw
import os
import operator
 
gdal.UseExceptions()
 
# This function will convert the rasterized clipper shapefile
# to a mask for use within GDAL.
def imageToArray(i):
 """
 Converts a Python Imaging Library array to a
 gdalnumeric image.
 """
 a=gdalnumeric.fromstring(i.tobytes(),'b')
 a.shape=i.im.size[1], i.im.size[0]
 return a
 
def arrayToImage(a):
 """
 Converts a gdalnumeric array to a
 Python Imaging Library Image.
 """
 i=Image.frombytes('L',(a.shape[1],a.shape[0]),
   (a.astype('b')).tobytes())
 return i
 
def world2Pixel(geoMatrix, x, y):
 """
 Uses a gdal geomatrix (gdal.GetGeoTransform()) to calculate
 the pixel location of a geospatial coordinate
 """
 ulX = geoMatrix[0]
 ulY = geoMatrix[3]
 xDist = geoMatrix[1]
 pixel = int((x - ulX) / xDist)
 line = int((ulY - y) / xDist)
 return (pixel, line)
 
#
# EDIT: this is basically an overloaded
# version of the gdal_array.OpenArray passing in xoff, yoff explicitly
# so we can pass these params off to CopyDatasetInfo
#
def OpenArray( array, prototype_ds = None, xoff=0, yoff=0 ):
 ds = gdal.Open( gdalnumeric.GetArrayFilename(array) )
 
 if ds is not None and prototype_ds is not None:
  if type(prototype_ds).__name__ == 'str':
   prototype_ds = gdal.Open( prototype_ds )
  if prototype_ds is not None:
   gdalnumeric.CopyDatasetInfo( prototype_ds, ds, xoff=xoff, yoff=yoff )
 return ds
 
def histogram(a, bins=range(0,256)):
 """
 Histogram function for multi-dimensional array.
 a = array
 bins = range of numbers to match
 """
 fa = a.flat
 n = gdalnumeric.searchsorted(gdalnumeric.sort(fa), bins)
 n = gdalnumeric.concatenate([n, [len(fa)]])
 hist = n[1:]-n[:-1]
 return hist
 
def stretch(a):
 """
 Performs a histogram stretch on a gdalnumeric array image.
 """
 hist = histogram(a)
 im = arrayToImage(a)
 lut = []
 for b in range(0, len(hist), 256):
  # step size
  step = reduce(operator.add, hist[b:b+256]) / 255
  # create equalization lookup table
  n = 0
  for i in range(256):
   lut.append(n / step)
   n = n + hist[i+b]
  im = im.point(lut)
 return imageToArray(im)
 
def main( shapefile_path, raster_path ):
 # Load the source data as a gdalnumeric array
 srcArray = gdalnumeric.LoadFile(raster_path)
 
 # Also load as a gdal image to get geotransform
 # (world file) info
 srcImage = gdal.Open(raster_path)
 geoTrans = srcImage.GetGeoTransform()
 
 # Create an OGR layer from a boundary shapefile
 shapef = ogr.Open(shapefile_path)
 lyr = shapef.GetLayer( os.path.split( os.path.splitext( shapefile_path )[0] )[1] )
 poly = lyr.GetNextFeature()
 
 # Convert the layer extent to image pixel coordinates
 minX, maxX, minY, maxY = lyr.GetExtent()
 ulX, ulY = world2Pixel(geoTrans, minX, maxY)
 lrX, lrY = world2Pixel(geoTrans, maxX, minY)
 
 # Calculate the pixel size of the new image
 pxWidth = int(lrX - ulX)
 pxHeight = int(lrY - ulY)
 
 clip = srcArray[:, ulY:lrY, ulX:lrX]
 
 #
 # EDIT: create pixel offset to pass to new image Projection info
 #
 xoffset = ulX
 yoffset = ulY
 print "Xoffset, Yoffset = ( %f, %f )" % ( xoffset, yoffset )
 
 # Create a new geomatrix for the image
 geoTrans = list(geoTrans)
 geoTrans[0] = minX
 geoTrans[3] = maxY
 
 # Map points to pixels for drawing the
 # boundary on a blank 8-bit,
 # black and white, mask image.
 points = []
 pixels = []
 geom = poly.GetGeometryRef()
 pts = geom.GetGeometryRef(0)
 for p in range(pts.GetPointCount()):
  points.append((pts.GetX(p), pts.GetY(p)))
 for p in points:
  pixels.append(world2Pixel(geoTrans, p[0], p[1]))
 rasterPoly = Image.new("L", (pxWidth, pxHeight), 1)
 rasterize = ImageDraw.Draw(rasterPoly)
 rasterize.polygon(pixels, 0)
 mask = imageToArray(rasterPoly)
 
 # Clip the image using the mask
 clip = gdalnumeric.choose(mask, \
  (clip, 0)).astype(gdalnumeric.uint8)
 
 # This image has 3 bands so we stretch each one to make them
 # visually brighter
 for i in range(3):
  clip[i,:,:] = stretch(clip[i,:,:])
 
 # Save new tiff
 #
 # EDIT: instead of SaveArray, let's break all the
 # SaveArray steps out more explicity so
 # we can overwrite the offset of the destination
 # raster
 #
 ### the old way using SaveArray
 #
 # gdalnumeric.SaveArray(clip, "OUTPUT.tif", format="GTiff", prototype=raster_path)
 #
 ###
 #
 gtiffDriver = gdal.GetDriverByName( 'GTiff' )
 if gtiffDriver is None:
  raise ValueError("Can't find GeoTiff Driver")
 gtiffDriver.CreateCopy( "beijing.tif",
  OpenArray( clip, prototype_ds=raster_path, xoff=xoffset, yoff=yoffset )
 )
 
 # Save as an 8-bit jpeg for an easy, quick preview
 clip = clip.astype(gdalnumeric.uint8)
 gdalnumeric.SaveArray(clip, "beijing.jpg", format="JPEG")
 
 gdal.ErrorReset()
 
 
if __name__ == '__main__':
 #shapefile_path, raster_path
 shapefile_path = 'beijing.shp'
 raster_path = 'world.tif'
 main( shapefile_path, raster_path )

补充知识:Python+GDAL | 读取矢量并写出txt

这篇文章主要描述了如何使用GDAL/OGR打开矢量文件、读取属性表,并将部分属性写出至txt。

代码

import ogr,sys,os
import numpy as np

os.chdir(r'E:\')

#设置driver,并打开矢量文件
driver = ogr.GetDriverByName('ESRI Shapefile')
ds = driver.Open('sites.shp', 0)
if ds is None:
  print("Could not open", 'sites.shp')
  sys.exit(1)
#获取图册
layer = ds.GetLayer()

#要素数量
numFeatures = layer.GetFeatureCount()
print("Feature count: "+str(numFeatures))

#获取范围
extent = layer.GetExtent()
print("Extent:", extent)
print("UL:", extent[0],extent[3])
print("LR:", extent[1],extent[2])

#获取要素
feature = layer.GetNextFeature()
ids = []
xs = []
ys = []
covers = []
#循环每个要素属性
while feature:
  #获取字段“id”的属性
  id = feature.GetField('id')
  #获取空间属性
  geometry = feature.GetGeometryRef()
  x = geometry.GetX()
  y = geometry.GetY()
  cover = feature.GetField('cover')
  ids.append(id)
  xs.append(x)
  ys.append(y)
  covers.append(cover)
  feature = layer.GetNextFeature()

data = [ids, xs, ys, covers]
data = np.array(data)
data = data.transpose()

#写出致txt
np.savetxt('myfile.txt',data, fmt='%s %s %s %s')
np.savetxt('myfile.csv',data, fmt='%s %s %s %s')

#释放文件空间
layer.ResetReading()
feature.Destroy()
ds.Destroy()

以上这篇在Python中用GDAL实现矢量对栅格的切割实例就是小编分享给大家的全部内容了,希望能给大家一个参考,也希望大家多多支持三水点靠木。

Python 相关文章推荐
python操作xml文件详细介绍
Jun 09 Python
在Python中封装GObject模块进行图形化程序编程的教程
Apr 14 Python
在Python中执行系统命令的方法示例详解
Sep 14 Python
学习Python selenium自动化网页抓取器
Jan 20 Python
Python 装饰器实现DRY(不重复代码)原则
Mar 05 Python
Python 中的Selenium异常处理实例代码
May 03 Python
Python中应该使用%还是format来格式化字符串
Sep 25 Python
Python3编码问题 Unicode utf-8 bytes互转方法
Oct 26 Python
python反编译学习之字节码详解
May 19 Python
python运用sklearn实现KNN分类算法
Oct 16 Python
pytorch 计算Parameter和FLOP的操作
Mar 04 Python
pytorch实现手写数字图片识别
May 20 Python
将 Ubuntu 16 和 18 上的 python 升级到最新 python3.8 的方法教程
Mar 11 #Python
利用Python裁切tiff图像且读取tiff,shp文件的实例
Mar 10 #Python
GDAL 矢量属性数据修改方式(python)
Mar 10 #Python
使用Python开发个京东上抢口罩的小实例(仅作技术研究学习使用)
Mar 10 #Python
python 获取当前目录下的文件目录和文件名实例代码详解
Mar 10 #Python
python爬虫开发之使用Python爬虫库requests多线程抓取猫眼电影TOP100实例
Mar 10 #Python
Django 404、500页面全局配置知识点详解
Mar 10 #Python
You might like
Extended CHM PHP 语法手册之 DIY
2006/10/09 PHP
随机头像PHP版
2006/10/09 PHP
一个php作的文本留言本的例子(一)
2006/10/09 PHP
PHP如何编写易读的代码
2007/07/10 PHP
Can't create/write to file 'C:\WINDOWS\TEMP\...MYSQL报错解决方法
2011/06/30 PHP
php计算指定目录下文件占用空间的方法
2015/03/13 PHP
Laravel框架源码解析之入口文件原理分析
2020/05/14 PHP
PhpStorm连接服务器并实现自动上传功能
2020/12/09 PHP
浅析JavaScript中的隐式类型转换
2013/12/05 Javascript
jQuery中:first-child选择器用法实例
2014/12/31 Javascript
jquery单击事件和双击事件冲突解决方案
2016/03/02 Javascript
Javascript 正则表达式校验数字的简单实例
2016/11/02 Javascript
vue.js树形组件之删除双击增加分支实例代码
2017/02/28 Javascript
ES6新特性六:promise对象实例详解
2017/04/21 Javascript
Bootstrap fileinput文件上传预览插件使用详解
2017/05/16 Javascript
微信小程序实现image组件图片自适应宽度比例显示的方法
2018/01/16 Javascript
Vue CLI 3搭建vue+vuex最全分析(推荐)
2018/09/27 Javascript
Postman参数化实现过程及原理解析
2020/08/13 Javascript
python实现删除文件与目录的方法
2014/11/10 Python
Python2.X/Python3.X中urllib库区别讲解
2017/12/19 Python
利用Python如何实现一个小说网站雏形
2018/11/23 Python
Python pip安装第三方库实现过程解析
2020/07/09 Python
MATLAB数学建模之画图汇总
2020/07/16 Python
Python+OpenCV图像处理——实现直线检测
2020/10/23 Python
HTML5 Canvas 旋转风车绘制
2017/08/18 HTML / CSS
耐克美国官网:Nike.com
2016/08/01 全球购物
一份Java笔试题
2012/02/21 面试题
告诉你怎样写创业计划书
2014/01/27 职场文书
销售代理协议书
2014/09/30 职场文书
个人四风问题对照检查材料
2014/10/01 职场文书
2014年村委会工作总结
2014/11/24 职场文书
廉洁自律个人总结
2015/02/14 职场文书
微信搭讪开场白
2015/05/28 职场文书
信用卡收入证明范本
2015/06/12 职场文书
校园运动会广播稿
2015/08/19 职场文书
springboot应用服务启动事件的监听实现
2022/04/06 Java/Android