commit 5b355be7955365bc62cf2c866df8d60fd3ca8aba (tree)
parent 5937f946697ee90802f91c43699efb3afe49dd42
Author: Motiejus Jakštys <motiejus@uber.com>
Date: Mon, 26 Apr 2021 10:12:46 +0300
douglas-peucker and visvalingam examples
Diffstat:
4 files changed, 90 insertions(+), 12 deletions(-)
diff --git a/IV/Makefile b/IV/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 $@
diff --git a/IV/layer2img.py b/IV/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)
- group2 is not None and group2.plot(ax=ax, **c2)
- group3 is not None and group3.plot(ax=ax, **c3)
+ group1 is not None and group1.plot(ax=ax, linewidth=.75, **c1)
+ group2 is not None and group2.plot(ax=ax, linewidth=.75, **c2)
+ group3 is not None and group3.plot(ax=ax, linewidth=.75, **c3)
ax.axis('off')
ax.margins(0, 0)
diff --git a/IV/mj-msc.tex b/IV/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
diff --git a/IV/tests-rivers.sql b/IV/tests-rivers.sql
@@ -22,7 +22,7 @@ begin
end
$$ language plpgsql;
-delete from wm_visuals where name in ('salvis');
+delete from wm_visuals where name like 'salvis%';
insert into wm_visuals(name, way) values('salvis', (
select st_intersection(
(select st_union(way) from wm_rivers where name in ('Šalčia', 'Visinčia')),
@@ -38,6 +38,23 @@ insert into wm_visuals(name, way) values('salvis', (
do $$
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;
secs bigint;
begin
