GDAL WriteArray 问题

Question

我正在使用Python的GDAL库把栅格数据写入一个.tif文件。以下是我的代码：

import numpy, sys
from osgeo import gdal, utils
from osgeo.gdalconst import *

# register all of the GDAL drivers
gdal.AllRegister()

# open the image
inDs = gdal.Open("C:\\Documents and Settings\\patrick\\Desktop\\tiff elevation\\EBK1KM\\color_a1.tif",GDT_UInt16)
if inDs is None:
  print "couldn't open input dataset"
  sys.exit(1)
else:
  print "opening was successful!"
cols = inDs.RasterXSize
rows = inDs.RasterYSize
bands =  inDs.RasterCount
driver = inDs.GetDriver()
driver.Create("C:\\Documents and Settings\\patrick\\Desktop\\tiff elevation\\EBK1KM\\newfile.tif",cols,rows,3,GDT_UInt16)
outDs = gdal.Open("C:\\Documents and Settings\\patrick\\Desktop\\tiff elevation\\EBK1KM\\newfile.tif")

if outDs is None:
  print "failure to create new file"
  sys.exit(1)


outBand1 = outDs.GetRasterBand(1)
outBand2 = outDs.GetRasterBand(2)
outBand3 = outDs.GetRasterBand(3)
data1 = inDs.GetRasterBand(1).ReadAsArray()
data2 = inDs.GetRasterBand(2).ReadAsArray()
data3 = inDs.GetRasterBand(3).ReadAsArray()

outBand1.WriteArray(data1,0,0)
outBand2.WriteArray(data2,0,0)
outBand3.WriteArray(data3,0,0)

print "before closing out the file"
print outDs.GetRasterBand(1).ReadAsArray(700,700,5,5)
print outDs.GetRasterBand(2).ReadAsArray(700,700,5,5)
print outDs.GetRasterBand(3).ReadAsArray(700,700,5,5)

outDs.SetProjection(inDs.GetProjection())
outDs.SetGeoTransform(inDs.GetGeoTransform())

outDs = None
outDs = gdal.Open("C:\\Documents and Settings\\patrick\\Desktop\\tiff elevation\\EBK1KM\\newfile.tif")
print "after reopening"
print outDs.GetRasterBand(1).ReadAsArray(700,700,5,5)
print outDs.GetRasterBand(2).ReadAsArray(700,700,5,5)
print outDs.GetRasterBand(3).ReadAsArray(700,700,5,5)

在关闭和重新打开输出数据集之间，得到的结果是不同的：

before closing out the file
[[ 36  35  55 121   0]
 [ 54   0 111 117   0]
 [  0 117 152  56   0]
 [ 89 122  56   0   0]
 [102 107   0  25  53]]
[[ 68  66 126 200   0]
 [ 78   0 166 157   0]
 [  0 235 203  70   0]
 [229 251 107   0   0]
 [241 203   0  42 121]]
[[0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]]
after reopening
[[0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]]
[[0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]]
[[0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 0 0 0]]

我是不是漏掉了什么命令，导致文件没有在把变量设置为None之前被写入和保存？我尝试添加了以下两条命令，但都没有成功：

outband1.FlushCache()
outDs.FlushCache()

Answer 1

你不需要先Create再Open一个栅格文件（你之前是用GA_ReadOnly来读取的）。而且一开始也不需要调用gdal.AllRegister()，因为在你把GDAL加载到Python时，这个函数已经被调用过了（可以参考这个栅格API教程）。

接下来是之前提到的一些内容（做了一些修改）：

# Create a new raster data source
outDs = driver.Create(out_fname, cols, rows, 3, gdal.GDT_UInt16)

# Write metadata
outDs.SetGeoTransform(inDs.GetGeoTransform())
outDs.SetProjection(inDs.GetProjection())

# Write raster data sets
for i in range(3):
    outBand = outDs.GetRasterBand(i + 1)
    outBand.WriteArray(data[i])

# Close raster file
outDs = None

有时候我会加上这个步骤，以确保文件完全释放，并防止遇到一些常见问题：

del outDs, outBand