Zusammenfassung
Defines a group or block of pixels to include for raster processing. The PixelBlockCollection object is made up of one or more PixelBlock objects.
Diskussion
The PixelBlock object defines a block of pixels within a raster to use for processing. It is used in conjunction with the PixelBlockCollection object to iterate through one or more large rasters for processing.
Syntax
PixelBlock (data, extent)
| Parameter | Erläuterung | Datentyp |
data | A NumPy array containing the pixel values for the pixel block. If the raster is not multidimensional, the shape of the array should be (rows, columns, bands). If the raster is multidimensional, the shape of the array should be (slices, rows, columns, bands). | NumPyArray |
extent | The spatial extent of the pixel block. | Extent |
Eigenschaften
| Eigenschaft | Erläuterung | Datentyp |
| cell_size (Schreibgeschützt) | The cell size of the pixels in the pixel block. This is a tuple containing the cell size in the x-direction and the y-direction (x-size, y-size). | tuple |
| tlc (Schreibgeschützt) | The coordinates of the pixel block's top left corner. | Point |
| spatial_reference (Schreibgeschützt) | The spatial reference of the pixel block. | SpatialReference |
Methodenübersicht
| Methode | Erläuterung |
| getData () | Returns the NumPy array within the pixel block. |
Methoden
getData ()
| Datentyp | Erläuterung |
| NumPyArray | The NumPy array object from the pixel block. |
Codebeispiel
Iterates through pixel blocks to calculate the total area of forest in a land cover raster.
import arcpy
# Specify the input raster
in_raster = arcpy.Raster("landcover.tif")
# Create a PixelBlockCollection
blockCollection = arcpy.ia.PixelBlockCollection(
in_raster, pixel_block_size = (512, 512), nodata_to_values = -1)
forest_cell_count = 0
# Iterate through each PixelBlock
try:
while True:
pixelblock = next(blockCollection)
np_array = pixelblock.getData()
forest_cell_count+= np.count_nonzero(np_array == 1) # value = 1 is forest class
except StopIteration:
pass
print ("total forest pixels : " + str(forest_cell_count))