Tool for overzooming individual tiles (#121)

* Starting work on overzooming

* Factor clipping out of geometry.cpp to simplify linkage

* Pull out more geometry functions into now-badly-named clip.cpp

* Not surprisingly, there is a bug

* Found the bug

* Make indent

* Pass attributes through

* Make formatting more consistent

* Fix typos in comments

* Fix the typos better

* Add tippecanoe-overzoom to the install list

* Give overzoom a predictable exit status

* Forgot to translate to and from polygon ring closepaths

* Fix geometry collapse at z21

* Add attribute stripping; don't generate layers if they have no features

* Add docs for tippecanoe-overzoom (as it will be, not as it is)

* Change overzoom to accept input and output files as arguments

* Working on overzooming tests

* Oops

* Hook up and test the detail and buffer options, and the empty-tile case

* Also test attribute stripping

* Fix error message

* Update changelog and version

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 2.29.0
+
+* Add tippecanoe-overzoom tool
+
 # 2.28.1
 
 * Allow --set-attribute to override an existing attribute value

Makefile

@@ -29,17 +29,18 @@ else
 	FINAL_FLAGS := -g $(WARNING_FLAGS) $(DEBUG_FLAGS)
 endif
 
-all: tippecanoe tippecanoe-enumerate tippecanoe-decode tile-join unit tippecanoe-json-tool
+all: tippecanoe tippecanoe-enumerate tippecanoe-decode tile-join unit tippecanoe-json-tool tippecanoe-overzoom
 
 docs: man/tippecanoe.1
 
-install: tippecanoe tippecanoe-enumerate tippecanoe-decode tile-join tippecanoe-json-tool
+install: tippecanoe tippecanoe-enumerate tippecanoe-decode tile-join tippecanoe-json-tool tippecanoe-overzoom
 	mkdir -p $(PREFIX)/bin
 	mkdir -p $(MANDIR)
 	cp tippecanoe $(PREFIX)/bin/tippecanoe
 	cp tippecanoe-enumerate $(PREFIX)/bin/tippecanoe-enumerate
 	cp tippecanoe-decode $(PREFIX)/bin/tippecanoe-decode
 	cp tippecanoe-json-tool $(PREFIX)/bin/tippecanoe-json-tool
+	cp tippecanoe-overzoom $(PREFIX)/bin/tippecanoe-overzoom
 	cp tile-join $(PREFIX)/bin/tile-join
 	cp man/tippecanoe.1 $(MANDIR)/tippecanoe.1
 
@@ -57,7 +58,7 @@ C = $(wildcard *.c) $(wildcard *.cpp)
 INCLUDES = -I/usr/local/include -I.
 LIBS = -L/usr/local/lib
 
-tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o projection.o memfile.o mvt.o serial.o main.o text.o dirtiles.o pmtiles_file.o plugin.o read_json.o write_json.o geobuf.o flatgeobuf.o evaluator.o geocsv.o csv.o geojson-loop.o json_logger.o visvalingam.o compression.o
+tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o projection.o memfile.o mvt.o serial.o main.o text.o dirtiles.o pmtiles_file.o plugin.o read_json.o write_json.o geobuf.o flatgeobuf.o evaluator.o geocsv.o csv.o geojson-loop.o json_logger.o visvalingam.o compression.o clip.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 tippecanoe-enumerate: enumerate.o
@@ -75,6 +76,9 @@ tippecanoe-json-tool: jsontool.o jsonpull/jsonpull.o csv.o text.o geojson-loop.o
 unit: unit.o text.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
+tippecanoe-overzoom: overzoom.o mvt.o clip.o
+	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
+
 -include $(wildcard *.d)
 
 %.o: %.c
@@ -87,12 +91,12 @@ clean:
 	rm -f ./tippecanoe ./tippecanoe-* ./tile-join ./unit *.o *.d */*.o */*.d tests/**/*.mbtiles tests/**/*.check
 
 indent:
-	clang-format -i -style="{BasedOnStyle: Google, IndentWidth: 8, UseTab: Always, AllowShortIfStatementsOnASingleLine: false, ColumnLimit: 0, ContinuationIndentWidth: 8, SpaceAfterCStyleCast: true, IndentCaseLabels: false, AllowShortBlocksOnASingleLine: false, AllowShortFunctionsOnASingleLine: false, SortIncludes: false}" $(C) $(H)
+	clang-format -i -style="{BasedOnStyle: Google, IndentWidth: 8, UseTab: Always, AllowShortIfStatementsOnASingleLine: false, ColumnLimit: 0, ContinuationIndentWidth: 8, SpaceAfterCStyleCast: true, IndentCaseLabels: false, AllowShortBlocksOnASingleLine: false, AllowShortFunctionsOnASingleLine: false, SortIncludes: false}" $(filter-out flatgeobuf.cpp,$(C)) $(H)
 
 TESTS = $(wildcard tests/*/out/*.json)
 SPACE = $(NULL) $(NULL)
 
-test: tippecanoe tippecanoe-decode $(addsuffix .check,$(TESTS)) raw-tiles-test parallel-test pbf-test join-test enumerate-test decode-test join-filter-test unit json-tool-test allow-existing-test csv-test layer-json-test pmtiles-test decode-pmtiles-test
+test: tippecanoe tippecanoe-decode $(addsuffix .check,$(TESTS)) raw-tiles-test parallel-test pbf-test join-test enumerate-test decode-test join-filter-test unit json-tool-test allow-existing-test csv-test layer-json-test pmtiles-test decode-pmtiles-test overzoom-test
 	./unit
 
 suffixes = json json.gz
@@ -266,6 +270,22 @@ enumerate-test:
 	cmp tests/ne_110m_admin_0_countries/out/enum.check tests/ne_110m_admin_0_countries/out/enum
 	rm tests/ne_110m_admin_0_countries/out/enum.mbtiles tests/ne_110m_admin_0_countries/out/enum.check
 
+overzoom-test: tippecanoe-overzoom
+	# Basic operation
+	./tippecanoe-overzoom -o tests/pbf/13-1310-3166.pbf tests/pbf/11-327-791.pbf 11/327/791 13/1310/3166
+	./tippecanoe-decode tests/pbf/13-1310-3166.pbf 13 1310 3166 > tests/pbf/13-1310-3166.pbf.json.check
+	cmp tests/pbf/13-1310-3166.pbf.json.check tests/pbf/13-1310-3166.pbf.json
+	rm tests/pbf/13-1310-3166.pbf tests/pbf/13-1310-3166.pbf.json.check
+	# Different detail and buffer, and attribute stripping
+	./tippecanoe-overzoom -d8 -b30 -y NAME -y name -y scalerank -o tests/pbf/13-1310-3166-8-30.pbf tests/pbf/11-327-791.pbf 11/327/791 13/1310/3166
+	./tippecanoe-decode tests/pbf/13-1310-3166-8-30.pbf 13 1310 3166 > tests/pbf/13-1310-3166-8-30.pbf.json.check
+	cmp tests/pbf/13-1310-3166-8-30.pbf.json.check tests/pbf/13-1310-3166-8-30.pbf.json
+	rm tests/pbf/13-1310-3166-8-30.pbf tests/pbf/13-1310-3166-8-30.pbf.json.check
+	# No features in child tile
+	./tippecanoe-overzoom -o tests/pbf/14-2616-6331.pbf tests/pbf/11-327-791.pbf 11/327/791 14/2616/6331
+	cmp tests/pbf/14-2616-6331.pbf /dev/null
+	rm tests/pbf/14-2616-6331.pbf
+
 join-test: tile-join
 	./tippecanoe -q -f -z12 -o tests/join-population/tabblock_06001420.mbtiles -YALAND10:'Land area' -L'{"file": "tests/join-population/tabblock_06001420.json", "description": "population"}'
 	./tippecanoe -q -f -Z5 -z10 -o tests/join-population/macarthur.mbtiles -l macarthur tests/join-population/macarthur.json

README.md

@@ -960,3 +960,25 @@ Join block geometries to employment attributes:
 ```
 $ tippecanoe-json-tool -c in_wac_S000_JT00_2015.csv tl_2010_18157_tabblock10.sort.json > blocks-wac.json
 ```
+
+tippecanoe-overzoom
+===================
+
+The `tippecanoe-overzoom` utility creates a vector tile from one of its parent tiles,
+clipping and scaling the geometry from the parent tile and excluding features that
+are clipped away. The idea is that if you create very high resolution tiles
+(using `--extra-detail`) at a moderate zoom level, you can use `tippecanoe-overzoom`
+to turn those into moderate detail tiles at high zoom levels, for the benefit of
+renderers that cannot internally overzoom high-resolution tiles without losing
+some of the precision. Running:
+
+    tippecanoe-overzoom -o out.mvt.gz inz/inx/iny outz/outx/outy in.mvt.gz
+
+reads tile `inz/inx/iny` of `in.mvt.gz` and produces tile `outz/outx/outy` of `out.mvt.gz`.
+
+### Options
+
+ * `-b` *buffer*: Set the tile buffer in the output tile (default 5)
+ * `-d` *detail*: Set the detail of the output tile (default 12)
+ * `-y` *attribute*: Retain the specified *attribute* in the output features. All attributes that are not named in a `-y` option will be removed.
+