Add custom simplification option

Author: jstcki

Makefile

@@ -20,6 +20,10 @@ ENCODING = utf8
 
 CONTOUR_INTERVAL = 500
 
+ifndef SIMPLIFY
+	SIMPLIFY = $(if $(REPROJECT),1e-9,.5)
+endif
+
 all: topo
 
 topo: node_modules \
@@ -387,7 +391,7 @@ topo/%.json: build/%.json
 		$(if $(REPROJECT),,--width=$(WIDTH) --height=$(HEIGHT) --margin=$(MARGIN)) \
 		--no-pre-quantization \
 		--post-quantization=1e5 \
-		--simplify $(if $(REPROJECT),1e-9,.5) \
+		--simplify=$(SIMPLIFY) \
 		$(if $(PROPERTIES),-p $(PROPERTIES),) \
 		-- $<
 
@@ -398,7 +402,7 @@ topo/%-municipalities-lakes.json: build/%-municipalities.json build/%-lakes.json
 		$(if $(REPROJECT),,--width=$(WIDTH) --height=$(HEIGHT) --margin=$(MARGIN)) \
 		--no-pre-quantization \
 		--post-quantization=1e5 \
-		--simplify $(if $(REPROJECT),1e-9,.5) \
+		--simplify=$(SIMPLIFY) \
 		$(if $(PROPERTIES),-p $(PROPERTIES),) \
 		-- $^
 
@@ -409,7 +413,7 @@ topo/ch-%-lakes.json: build/ch-%.json build/ch-lakes.json
 		$(if $(REPROJECT),,--width=$(WIDTH) --height=$(HEIGHT) --margin=$(MARGIN)) \
 		--no-pre-quantization \
 		--post-quantization=1e5 \
-		--simplify $(if $(REPROJECT),1e-9,.5) \
+		--simplify=$(SIMPLIFY) \
 		$(if $(PROPERTIES),-p $(PROPERTIES),) \
 		-- $^
 
@@ -420,7 +424,7 @@ topo/ch.json: $(addprefix build/ch-,$(addsuffix .json,municipalities cantons dis
 		$(if $(REPROJECT),,--width=$(WIDTH) --height=$(HEIGHT) --margin=$(MARGIN)) \
 		--no-pre-quantization \
 		--post-quantization=1e5 \
-		--simplify $(if $(REPROJECT),1e-9,.5) \
+		--simplify=$(SIMPLIFY) \
 		$(if $(PROPERTIES),-p $(PROPERTIES),) \
 		-- $^
 
@@ -456,7 +460,7 @@ topo/ch-plz.json: build/ch/plz.shp
 	node_modules/.bin/topojson \
 		-o $@ \
 		$(if $(REPROJECT),,--width $(WIDTH) --height $(HEIGHT) --margin $(MARGIN)) \
-		--simplify $(if $(REPROJECT),1e-9,.5) \
+		--simplify=$(SIMPLIFY) \
 		--id-property +PLZ \
 		-- plz=$<
 
@@ -522,7 +526,7 @@ topo/ch-contours.json: build/ch/contours.shp
 	mkdir -p $(dir $@)
 	node_modules/.bin/topojson \
 		$(if $(REPROJECT),,--width $(WIDTH) --height $(HEIGHT) --margin $(MARGIN)) \
-		--simplify $(if $(REPROJECT),1e-9,.5) \
+		--simplify=$(SIMPLIFY) \
 		--id-property=+elev \
 		-- contours=$< \
 	| node_modules/.bin/topojson-group \

README.md

@@ -113,6 +113,14 @@ Municipality boundaries from 2013 and 2014 are also available. If you want bound
 
     make topo/ch-municipalities.json YEAR=2013
 
+## Custom Simplification
+
+To use a custom simplification, define the `SIMPLIFY` variable. For example, to create a really blocky version of Switzerland:
+
+    make topo/ch-country.json SIMPLIFY=400
+
+*Note:* The simplify parameter has [different meanings depending on the coordinate system](https://github.com/mbostock/topojson/wiki/Command-Line-Reference#simplification).
+
 ## Other Modifications
 
 For everything else you can modify the `Makefile` or run `ogr2ogr` and `topojson` directly. Mike Bostock's tutorial [Let's Make a Map](http://bost.ocks.org/mike/map/), the [TopoJSON wiki](https://github.com/mbostock/topojson/wiki), and [ogr2ogr documentation](http://www.gdal.org/ogr2ogr.html) should cover most of your needs.