NumPyArrayToRaster (arcpy)

摘要

将 NumPy 数组转换为栅格。

讨论

所生成的栅格数据集的大小和数据类型取决于输入数组。

拥有 x_cell_size 和 y_cell_size 参数可支持矩形像元。

注:

不支持 Esri Grid 格式的矩形像元大小。

NumpyArrayToRaster 支持将多维 NumPy 数组直接转换为多波段栅格。

1. 如果输入数组具有两个维度，则会返回单波段栅格，其栅格大小由这两个维度（行、列）定义。
2. 如果输入数组具有三个维度，则返回多波段栅格，其波段数等于第一维的长度，而栅格大小由第二维和第三维（波段、行、列）定义。
   • 如果输入数组具有三个维度并且第一维的大小为 1，则会返回单波段栅格。

此函数支持以下地理处理环境设置：

输出坐标系、范围、捕捉栅格、当前工作空间、临时工作空间

语法

NumPyArrayToRaster (in_array, {lower_left_corner}, {x_cell_size}, {y_cell_size}, {value_to_nodata})

参数	说明	数据类型
in_array	The NumPy array to convert to a raster. A two- or three-dimensional NumPy array is required.	NumPyArray
lower_left_corner	A Point object defining the lower left corner of the output raster in map units. The default will set the lower left corner to coordinate (0.0, 0.0). (默认值为 None)	Point
x_cell_size	The cell size in the x direction specified in map units. The input can be a specified cell size (type: double) value, or a raster. When a dataset is specified, the x cell size of that dataset is used for the x cell size of the output raster. If only the x_cell_size is identified and not the y_cell_size, a square cell will result with the specified size. If neither x_cell_size nor y_cell_size is specified, a default of 1.0 will be used for both the x and y cell size. (默认值为 1.0)	Double
y_cell_size	The cell size in the y direction specified in map units. The input can be a specified cell size (type: double) value, or a raster. When a dataset is specified, the x cell size of that dataset is used for the y cell size of the output raster. If only the y_cell_size is identified and not the x_cell_size, a square cell will result with the specified size. If neither x_cell_size nor y_cell_size is specified, a default of 1.0 will be used for both the x and y cell size. (默认值为 1.0)	Double
value_to_nodata	The value in the NumPy array to assign to NoData in the output raster. If no value is specified for value_to_nodata, there will not be any NoData values in the resulting raster. (默认值为 None)	Double

返回值

数据类型	说明
Raster	输出栅格。

代码实例

NumPyArrayToRaster 示例 1

从随机生成的 NumPy 数组创建一个新栅格。

import arcpy
import numpy

# Create a simple array from scratch using random values
myArray = numpy.random.random_integers(0,100,2500)
myArray.shape = (50,50)

# Convert array to a geodatabase raster
myRaster = arcpy.NumPyArrayToRaster(myArray,x_cell_size=1)
myRaster.save("C:/output/fgdb.gdb/myRandomRaster")

NumPyArrayToRaster 示例 2

块将对输入多波段栅格进行处理并计算所有波段的像元统计数据。该脚本将多波段栅格转换为三维 NumPy 数组，并通过将该数组划分为数据块的方式对其进行处理。接下来，该脚本将计算块中所有行的平均值，将块 numpy 数组转换成栅格，并通过镶嵌重新组合波段。已创建新的多波段栅格。

# Note that, if the input raster is multiband, the data blocks will also be
# multiband, having dimensions (bands, rows, columns).  Otherwise, they will
# have dimensions (rows, columns).

import arcpy
import numpy
import os

# Input raster
filein = os.path.join(os.getcwd(),r"input\input.tif")

# Output raster (after processing)
fileout = os.path.join(os.getcwd(),r"output\blockprocessingrdb22.tif")

# Size of processing data block
# where memorysize = datatypeinbytes*nobands*blocksize^2
blocksize = 512

# ----------------------------------------------------------------------------
# Create raster object from file
myRaster = arcpy.Raster(filein)

# Set environmental variables for output
arcpy.env.overwriteOutput = True
arcpy.env.outputCoordinateSystem = filein
arcpy.env.cellSize = filein

# Loop over data blocks
filelist = []
blockno = 0
for x in range(0, myRaster.width, blocksize):
    for y in range(0, myRaster.height, blocksize):

        # Lower left coordinate of block (in map units)
        mx = myRaster.extent.XMin + x * myRaster.meanCellWidth
        my = myRaster.extent.YMin + y * myRaster.meanCellHeight
        # Upper right coordinate of block (in cells)
        lx = min([x + blocksize, myRaster.width])
        ly = min([y + blocksize, myRaster.height])
        #   noting that (x, y) is the lower left coordinate (in cells)

        # Extract data block
        myData = arcpy.RasterToNumPyArray(myRaster, arcpy.Point(mx, my),
                                          lx-x, ly-y)

        # PROCESS DATA BLOCK -----------------------------
        # e.g. Calculate mean of each cell of all bands.
        myData -= numpy.mean(myData, axis=0, keepdims=True)
        # ------------------------------------------------

        # Convert data block back to raster
        myRasterBlock = arcpy.NumPyArrayToRaster(myData, arcpy.Point(mx, my),
                                                 myRaster.meanCellWidth,
                                                 myRaster.meanCellHeight)

        # Save on disk temporarily as 'filename_#.ext'
        filetemp = ('_%i.' % blockno).join(fileout.rsplit('.',1))
        myRasterBlock.save(filetemp)

        # Maintain a list of saved temporary files
        filelist.append(filetemp)
        blockno += 1

# Mosaic temporary files
arcpy.Mosaic_management(';'.join(filelist[1:]), filelist[0])
if arcpy.Exists(fileout):
    arcpy.Delete_management(fileout)
arcpy.Rename_management(filelist[0], fileout)

# Remove temporary files
for fileitem in filelist:
    if arcpy.Exists(fileitem):
        arcpy.Delete_management(fileitem)

# Release raster objects from memory
del myRasterBlock
del myRaster
# ----------------------------------------------------------------------------