douglas-peucker and visvalingam examples

Makefile

@@ -28,7 +28,11 @@ FIGURES = \
 RIVERS = \
 		 salvis-25k \
 		 salvis-50k \
-		 salvis-250k
+		 salvis-250k \
+		 salvis-douglas-64-50k \
+		 salvis-visvalingam-64-50k \
+		 salvis-douglas-64-chaikin-50k \
+		 salvis-visvalingam-64-chaikin-50k
 
 #################################
 # The thesis, publishable version
@@ -126,6 +130,23 @@ salvis-50k_WIDTHDIV = 2
 salvis-250k_1SELECT = wm_visuals where name='salvis'
 salvis-250k_WIDTHDIV = 10
 
+#salvis-douglas-64-50k_1SELECT = wm_visuals where name='salvis'
+salvis-douglas-64-50k_2SELECT = wm_visuals where name='salvis-douglas-64'
+salvis-douglas-64-50k_WIDTHDIV = 2
+
+#salvis-visvalingam-64-50k_1SELECT = wm_visuals where name='salvis'
+salvis-visvalingam-64-50k_2SELECT = wm_visuals where name='salvis-visvalingam-64'
+salvis-visvalingam-64-50k_WIDTHDIV = 2
+
+salvis-douglas-64-chaikin-50k_1SELECT = wm_visuals where name='salvis'
+salvis-douglas-64-chaikin-50k_2SELECT = wm_visuals where name='salvis-douglas-64-chaikin'
+salvis-douglas-64-chaikin-50k_WIDTHDIV = 2
+
+salvis-visvalingam-64-chaikin-50k_1SELECT = wm_visuals where name='salvis'
+salvis-visvalingam-64-chaikin-50k_2SELECT = wm_visuals where name='salvis-visvalingam-64-chaikin'
+salvis-visvalingam-64-chaikin-50k_WIDTHDIV = 2
+
+
 .faux_test-rivers: tests-rivers.sql wm.sql Makefile .faux_db
 	bash db -v scaledwidth=$(SCALEDWIDTH) -f $<
 	touch $@

layer2img.py

@@ -24,7 +24,7 @@ def inch(cm):
 def parse_args():
     parser = argparse.ArgumentParser(
             description='Convert a geometry to an image')
-    parser.add_argument('--group1-select', required=True)
+    parser.add_argument('--group1-select')
     parser.add_argument('--group1-linestyle')
 
     simplify = parser.add_mutually_exclusive_group()
@@ -91,9 +91,9 @@ def main():
     fig, ax = plt.subplots()
     fig.set_figwidth(inch(width))
 
-    group1 is not None and group1.plot(ax=ax, **c1)
+    group1 is not None and group1.plot(ax=ax, linewidth=.75, **c1)
-    group2 is not None and group2.plot(ax=ax, **c2)
+    group2 is not None and group2.plot(ax=ax, linewidth=.75, **c2)
-    group3 is not None and group3.plot(ax=ax, **c3)
+    group3 is not None and group3.plot(ax=ax, linewidth=.75, **c3)
 
     ax.axis('off')
     ax.margins(0, 0)

mj-msc.tex

@@ -34,6 +34,8 @@
 % does not require minted
 \usepackage{verbatim}
 \newcommand{\inputcode}[2]{\verbatiminput{#2}}
+\usepackage{setspace}
+\doublespacing
 \fi
 
 \input{version.inc}
@@ -192,12 +194,6 @@ thus convenient to analyze for both small and large scale generalization.
     \label{fig:salvis-25}
 \end{figure}
 
-Same rivers, unprocessed, but with higher density (scales 1:50000 and 1:250000)
-are depicted in figure~\ref{fig:salvis-50-250}. Some river features are so
-compact that a reasonably thin line depicting the river is overlapping with
-itself, creating a thicker line in print. As a result, generalization for this
-river for a smaller scale is worthy.
-
 \begin{figure}[h]
     \centering
     \begin{subfigure}[b]{.49\textwidth}
@@ -214,6 +210,50 @@ river for a smaller scale is worthy.
     \label{fig:salvis-50-250}
 \end{figure}
 
+Same rivers, unprocessed, but with higher density (scales 1:50000 and 1:250000)
+are depicted in figure~\onpage{fig:salvis-50-250}. Some river features are so
+compact that a reasonably thin line depicting the river is touching itself,
+creating a thicker line. As a result, generalization for this river for a
+smaller scale is worthy.
+
+\begin{figure}[h]
+    \centering
+    \begin{subfigure}[b]{.49\textwidth}
+        \includegraphics[width=\textwidth]{salvis-douglas-64-50k}
+        \caption{Using {\DP}}
+    \end{subfigure}
+    \hfill
+    \begin{subfigure}[b]{.49\textwidth}
+        \includegraphics[width=\textwidth]{salvis-visvalingam-64-50k}
+        \caption{Using {\VW}}
+    \end{subfigure}
+    \caption{Generalized using classical algorithms (1:50000).}
+    \label{fig:salvis-generalized-50k}
+\end{figure}
+
+
+Figure~\onpage{fig:salvis-generalized-50k} illustrates the same river bend, but
+generalized using {\DP} and {\VW} algorithms. The resulting lines are jagged,
+thus the resulting line looks unlike a real river. To smoothen the jaggedness,
+traditionally, Chaikin's\cite{chaikin1974algorithm} is applied after
+generalization, illustrated in
+figure~\onpage{fig:salvis-generalized-chaikin-50k}.
+
+\begin{figure}[h]
+    \centering
+    \begin{subfigure}[b]{.49\textwidth}
+        \includegraphics[width=\textwidth]{salvis-douglas-64-chaikin-50k}
+        \caption{Using {\DP} and Chaikin's}
+    \end{subfigure}
+    \hfill
+    \begin{subfigure}[b]{.49\textwidth}
+        \includegraphics[width=\textwidth]{salvis-visvalingam-64-chaikin-50k}
+        \caption{Using {\VW} and Chaikin's}
+    \end{subfigure}
+    \caption{Generalized and smoothened river (1:50000).}
+    \label{fig:salvis-generalized-chaikin-50k}
+\end{figure}
+
 \subsubsection{Modern approaches}
 
 Due to their simplicity and ubiquity, {\DP} and {\VW} have been established as

tests-rivers.sql

@@ -22,7 +22,7 @@ begin
 end
 $$ language plpgsql;
 
-delete from wm_visuals where name in ('salvis');
+delete from wm_visuals where name like 'salvis%';
 insert into wm_visuals(name, way) values('salvis', (
     select st_intersection(
       (select st_union(way) from wm_rivers where name in ('Šalčia', 'Visinčia')),
@@ -36,6 +36,23 @@ insert into wm_visuals(name, way) values('salvis', (
     )
 ));
 
+do $$
+declare
+  i integer;
+  geom1 geometry;
+  geom2 geometry;
+begin
+  foreach i in array array[16, 64, 256] loop
+    geom1 = st_simplify((select way from wm_visuals where name='salvis'), i);
+    geom2 = st_simplifyvw((select way from wm_visuals where name='salvis'), i*i);
+    insert into wm_visuals(name, way) values
+      ('salvis-douglas-'     || i, geom1),
+      ('salvis-douglas-'     || i || '-chaikin', st_chaikinsmoothing(geom1, 5)),
+      ('salvis-visvalingam-' || i, geom2),
+      ('salvis-visvalingam-' || i || '-chaikin', st_chaikinsmoothing(geom2, 5));
+  end loop;
+end $$ language plpgsql;
+
 do $$
 declare
   npoints bigint;