from gdalconst import *
from osgeo import gdal
import osr
import sys
import copy

#叠加两个栅格图像（一个道路栅格图，一个土地利用类型图），两幅图像重叠的像元值都是第一个图像的值，
#未重叠的像元值还是土地利用类型图上的值，最终结果便是土地利用类型图上面多了道路信息。

roadFile = 'E:\\Exercise\\test\\grasstest\\road_rastercalc.tif'
landuseFile = 'E:\\Exercise\\test\\grasstest\\landuse.tif'
roadDs = gdal.Open(roadFile, GA_ReadOnly)
landuseDs = gdal.Open(landuseFile, GA_ReadOnly)
if roadDs is None:
  print 'Can not open ', roadFile
  sys.exit(1)

geotransform = roadDs.GetGeoTransform()
projection=roadDs.GetProjection()
cols = roadDs.RasterXSize
rows = roadDs.RasterYSize
roadBand = roadDs.GetRasterBand(1)
roadData = roadBand.ReadAsArray(0,0,cols,rows)
roadNoData = roadBand.GetNoDataValue()

landuseBand = landuseDs.GetRasterBand(1)
landuseData = landuseBand.ReadAsArray(0,0,cols,rows)
landuseNoData = landuseBand.GetNoDataValue()


result = landuseData

for i in range(0,rows):
  for j in range(0,cols):
    if(abs(roadData[i,j] - 20) < 0.0001):
      result[i,j] = 20
    if((abs(landuseData[i,j] - landuseNoData)>0.0001) and (abs(roadData[i,j] - roadNoData) < 0.0001)):
      result[i,j] = landuseData[i,j]
    if((abs(landuseData[i,j] - landuseNoData)<0.0001) and (abs(roadData[i,j] - roadNoData) < 0.0001)):
      result[i,j] = landuseNoData
#write result to disk
resultPath = 'E:\\Exercise\\test\\grasstest\\result_landuse.tif'

format = "GTiff"  
driver = gdal.GetDriverByName(format)
ds = driver.Create(resultPath, cols, rows, 1, GDT_Float32)
ds.SetGeoTransform(geotransform)
ds.SetProjection(projection)
ds.GetRasterBand(1).SetNoDataValue(landuseNoData)
ds.GetRasterBand(1).WriteArray(result)  
ds = None

print 'ok---------'