feat: add flag --merge-skip-blending to skip expensive blending in splitmerge (#1934)

Author: spwoodcock

contrib/mergepreview/mergepreview.py

@@ -116,7 +116,7 @@
         'BIGTIFF': 'IF_SAFER',
         'BLOCKXSIZE': 512,
         'BLOCKYSIZE': 512
-    })
+    }, args.merge_skip_blending)
 
 
     log.ODM_INFO("Wrote %s" % output_file)

opendm/config.py

@@ -828,6 +828,18 @@ def config(argv=None, parser=None):
                           'Options: %(choices)s. Default: '
                             '%(default)s'))
 
+    # TODO ideally the blending should be optimised so we don't need this param to skip it, e.g.
+    #   1. Only blend in a buffer zone around cutline edges (e.g., 100-200 pixels)
+    #   2. Skip blending for interior regions that are far from edges
+    #   3. This would require detecting which blocks intersect cutline boundaries
+    # We have block-based processing already in place in orthophoto.py, so need logic to determine
+    # if a block needs blending based on its proximity to cutlines
+    parser.add_argument('--merge-skip-blending',
+                        action=StoreTrue,
+                        nargs=0,
+                        default=False,
+                        help='During the orthophoto merging, skip expensive blending operation: %(default)s')
+
     parser.add_argument('--force-gps',
                     action=StoreTrue,
                     nargs=0,

opendm/orthophoto.py

@@ -265,7 +265,7 @@ def feather_raster(input_raster, output_raster, blend_distance=20):
 
         return output_raster
 
-def merge(input_ortho_and_ortho_cuts, output_orthophoto, orthophoto_vars={}):
+def merge(input_ortho_and_ortho_cuts, output_orthophoto, orthophoto_vars={}, merge_skip_blending=False):
     """
     Based on https://github.com/mapbox/rio-merge-rgba/
     Merge orthophotos around cutlines using a blend buffer.
@@ -334,6 +334,10 @@ def merge(input_ortho_and_ortho_cuts, output_orthophoto, orthophoto_vars={}):
     profile["bigtiff"] = orthophoto_vars.get('BIGTIFF', 'IF_SAFER')
     profile.update()
 
+    # Log here to avoid logging in each block processed
+    if merge_skip_blending:
+        log.ODM_INFO("Skipping second and third pass orthophoto blending, as --merge-skip-blending passed")
+
     # create destination file
     with rasterio.open(output_orthophoto, "w", **profile) as dstrast:
         dstrast.colorinterp = colorinterp
@@ -372,6 +376,11 @@ def merge(input_ortho_and_ortho_cuts, output_orthophoto, orthophoto_vars={}):
                 if np.count_nonzero(dstarr[-1]) == blocksize:
                     break
 
+            # Skip expensive blending operations if flag passed
+            if merge_skip_blending:
+                dstrast.write(dstarr, window=dst_window)
+                continue
+
             # Second pass, write all feathered rasters
             # blending the edges
             for src, _ in sources:

stages/splitmerge.py

@@ -262,7 +262,7 @@ def process(self, args, outputs):
                             os.remove(tree.odm_orthophoto_tif)
 
                         orthophoto_vars = orthophoto.get_orthophoto_vars(args)
-                        orthophoto.merge(all_orthos_and_ortho_cuts, tree.odm_orthophoto_tif, orthophoto_vars)
+                        orthophoto.merge(all_orthos_and_ortho_cuts, tree.odm_orthophoto_tif, orthophoto_vars, args.merge_skip_blending)
                         orthophoto.post_orthophoto_steps(args, merged_bounds_file, tree.odm_orthophoto_tif, tree.orthophoto_tiles, args.orthophoto_resolution,
                             reconstruction, tree, False)
                     elif len(all_orthos_and_ortho_cuts) == 1: