Python计算多幅图像栅格值的平均值

import os
import os.path
import gdal
import sys
from gdalconst import *
from osgeo import gdal
import osr
import numpy as np
#coding=utf-8

def WriteGTiffFile(filename, nRows, nCols, data,geotrans,proj, noDataValue, gdalType):#向磁盘写入结果文件
    format = "GTiff"   
    driver = gdal.GetDriverByName(format)
    ds = driver.Create(filename, nCols, nRows, 1, gdalType)
    ds.SetGeoTransform(geotrans)
    ds.SetProjection(proj)
    ds.GetRasterBand(1).SetNoDataValue(noDataValue)
    ds.GetRasterBand(1).WriteArray(data)    
    ds = None

def File():#遍历文件，读取数据，算出均值
    rows,cols,geotransform,projection,noDataValue = Readxy('E://work//EVI_Data_tif//20006.tif')
    #获取源文件的行，列，投影等信息，所有的源文件这些信息都是一致的
    print 'rows and cols is ',rows,cols
    filesum = [[0.0]*cols]*rows #栅格值和，二维数组
    average= [[0.0]*cols]*rows# 存放平均值，二维数组
    filesum=np.array(filesum)#转换类型为np.array
    average = np.array(average) 
    print 'the type of filesum',type(filesum)
    count=0
    rootdir = 'E:\work\EVI_Data_tif'
    for dirpath,filename,filenames in os.walk(rootdir):#遍历源文件
        for filename in filenames:
            if os.path.splitext(filename)[1] == '.tif':#判断是否为tif格式
                filepath = os.path.join(dirpath,filename)
                purename = filename.replace('.tif','') #获得除去扩展名的文件名，比如201013.tif，purename为201013               
                if purename[:4] == '2010':              #判断年份
                    filedata = [[0.0]*cols]*rows
                    filedata = np.array(filedata)
                    filedata = Read(filepath)           #将2010年的13幅图像数据存入filedata中
                    count+=1
                    np.add(filesum,filedata,filesum)    #求13幅图像相应栅格值的和
                    #print str(count)+'this is filedata',filedata
    print 'count is ',count    
    for i in range(0,rows):
        for j in range(0,cols):
            if(filesum[i,j]==noDataValue*count):        #处理图像中的noData
                average[i,j]=-9999
            else: 
                average[i,j]=filesum[i,j]*1.0/count     #求平均
    WriteGTiffFile("E:\\work\\result\\2010.tif", rows, cols, average,geotransform,projection, -9999, GDT_Float32) #写入结果文件           

def Readxy(RasterFile): #读取每个图像的信息     
    ds = gdal.Open(RasterFile,GA_ReadOnly)
    if ds is None:
        print 'Cannot open ',RasterFile
        sys.exit(1)
    cols = ds.RasterXSize
    rows = ds.RasterYSize
    band = ds.GetRasterBand(1)
    data = band.ReadAsArray(0,0,cols,rows)
    noDataValue = band.GetNoDataValue()
    projection=ds.GetProjection()
    geotransform = ds.GetGeoTransform()
    return rows,cols,geotransform,projection,noDataValue

def Read(RasterFile):#读取每个图像的信息
    ds = gdal.Open(RasterFile,GA_ReadOnly)    
    if ds is None:
        print 'Cannot open ',RasterFile
        sys.exit(1)
    cols = ds.RasterXSize
    rows = ds.RasterYSize
    band = ds.GetRasterBand(1)
    data = band.ReadAsArray(0,0,cols,rows)  
    return data    
if __name__ == "__main__":
    print"ok1"
    File()   
    print"ok2"