gdal raster polygonize: change --connectedness to --connect-diagonal-pixels (consistent with gdal raster sieve)

Author: rouault

apps/gdalalg_raster_polygonize.cpp

@@ -73,11 +73,10 @@ GDALRasterPolygonizeAlgorithm::GDALRasterPolygonizeAlgorithm()
     AddArg("attribute-name", 0, _("Name of the field with the pixel value"),
            &m_attributeName)
         .SetDefault(m_attributeName);
-    AddArg("connectedness", 0,
-           _("Whether to use 4-connectedness or 8-connectedness"),
-           &m_connectedness)
-        .SetChoices("4", "8")
-        .SetDefault(m_connectedness);
+
+    AddArg("connect-diagonal-pixels", 'c',
+           _("Consider diagonal pixels as connected"), &m_connectDiagonalPixels)
+        .SetDefault(m_connectDiagonalPixels);
 }
 
 /************************************************************************/
@@ -238,7 +237,7 @@ bool GDALRasterPolygonizeAlgorithm::RunImpl(GDALProgressFunc pfnProgress,
     }
 
     CPLStringList aosPolygonizeOptions;
-    if (m_connectedness == 8)
+    if (m_connectDiagonalPixels)
     {
         aosPolygonizeOptions.SetNameValue("8CONNECTED", "8");
     }

apps/gdalalg_raster_polygonize.h

@@ -51,7 +51,7 @@ class GDALRasterPolygonizeAlgorithm final : public GDALAlgorithm
     int m_band = 1;
     std::string m_outputLayerName = "polygonize";
     std::string m_attributeName = "DN";
-    int m_connectedness = 4;
+    bool m_connectDiagonalPixels = false;
 };
 
 //! @endcond

autotest/utilities/test_gdalalg_raster_polygonize.py

@@ -224,13 +224,13 @@ def test_gdalalg_raster_polygonize_int64():
     assert lyr.GetLayerDefn().GetFieldDefn(0).GetType() == ogr.OFTInteger64
 
 
-def test_gdalalg_raster_polygonize_connectedness():
+def test_gdalalg_raster_polygonize_connect_diagonal_pixels():
 
     alg = get_alg()
     alg["input"] = "../gcore/data/byte.tif"
     alg["output"] = ""
     alg["output-format"] = "MEM"
-    alg["connectedness"] = 8
+    alg["connect-diagonal-pixels"] = True
     assert alg.Run()
     ds = alg["output"].GetDataset()
     lyr = ds.GetLayerByName("polygonize")

doc/source/programs/gdal_raster_polygonize.rst

@@ -72,12 +72,13 @@ Standard options
 
     The name of the field to create (defaults to "DN").
 
-.. option:: --connectedness 4|8
+.. option:: -c, --connect-diagonal-pixels
 
-    Whether to use 4-connectedness or 8-connectedness. With 4-connectedness,
-    pixels will be included in the same output feature if they share a side.
-    With 8-connectedness, pixels will also be included in the same output
-    feature if they share a corner. Default is 4.
+    Consider diagonal pixels (pixels at the corners) as connected.
+    The default behavior is to only consider pixels that are touching the edges
+    as connected, which is the same as 4-connectivity. When this option is
+    selected, the algorithm will also consider pixels at the corners as connected,
+    which is the same as 8-connectivity.
 
 
 Advanced options