DM_shape_file_write.py

## @package python.demo.DM_shape_file_write
# 
# \brief create a polygon shape file with an used-defined attribute table.
# 
# Since shape files require at least one attribute column, the shape export class automatically adds an
# id attribute column if no user-defined attribute mapping (setAttributeMapping) is applied. Furthermore, the
# export class can optionally fill a attribute column with ascending numbers (starting from 0) by specifying
# the corresponding column index using 'idCounterIdx' in setAttributeMapping
# 
from opals import pyDM
 
# Create polygon and layout factory objects
pf = pyDM.PolygonFactory()
lf = pyDM.AddInfoLayoutFactory()
lf.addColumn(pyDM.ColumnSemantic.Id)  # internal shape object identifier. It's automatically set by the shape export
lf.addColumn(pyDM.ColumnType.uint32, "_RegionId")  # user-defined attribute "_RegionId" (type unsigned int)
layout = lf.getLayout()
 
filename = "export_test.shp"
 
def create_window(xmin, ymin, xmax, ymax):
    pf.addPoint(xmin, ymin)
    pf.addPoint(xmax, ymin)
    pf.addPoint(xmax, ymax)
    pf.addPoint(xmin, ymax)
    pf.closePart()
    return pf.getPolygon()
 
 
def set_attribute(obj, value):
    obj.setAddInfoView(layout, False)
    obj.info().set(1, value)
 
 
# Create table definition for the shape file
# Option 1: Based on layout (and optionally remove the leading underscore of user-defined attributes)
tableDef = pyDM.ShapeTableDefinition(layout, removeLeadingUnderscore=True)
# Option 2: Explicitly define name, type, width and decimals (for floating point types only) for each column
#           as four lists. Note: the with entries needs to be appropriately set for ALL data types. Also, make
#           sure that all lists have the same len.
tableDef2 = pyDM.ShapeTableDefinition(names=["Id", "RegionId"], types=[pyDM.ColumnType.uint32, pyDM.ColumnType.int32],
                                      widths=[4, 8], decimals=[0, 0])
 
# Create shape export with the
print(f"Open shape file '{filename}'")
exp = pyDM.ExportShape(filename)
exp.setAttributeMapping(layout, tableDef, idCounterIdx=0)   # use attribute column 0 as automatically filled counter
 
print("Write two polygons")
# output polygon windows 1
poly1 = create_window(0,0,10,10)
set_attribute(poly1, 30)
exp.write(poly1)
 
# output polygon windows 2
poly2 = create_window(30,20,50,25)
set_attribute(poly2, 35)
exp.write(poly2)
 
#close shape file
print("Close shape file")
exp.close()
 
print("Done")