commit 0131ef85d1f6ca42139e2024933dbe48ed5d541d (tree)
parent c452e595f00ef094758af94acae562460aa0f66e
Author: Motiejus Jakštys <desired.mta@gmail.com>
Date: Thu, 18 Jun 2020 10:38:05 +0300
wip chaikin
Diffstat:
4 files changed, 70 insertions(+), 5 deletions(-)
diff --git a/II/Referatas/Makefile b/II/Referatas/Makefile
@@ -2,6 +2,7 @@ CROSSING = 622916 6109267 626066 6111487 # xmin ymin xmax ymax
ZEIMENA_TOLERANCES = 128 256 512 1024 2048 4096
SINEWAVE_TOLERANCES = 2 16 32
CROSSING_TOLERANCES = 64 128 256
+CHAIKIN_CROSSING_TOLERANCES = 128 256
SINEWAVE_SIZE = 120x48
GEN1 = $(addsuffix .pdf, \
$(addprefix sinewave2_douglas_,$(SINEWAVE_TOLERANCES)) \
@@ -13,12 +14,15 @@ GEN2 = $(addsuffix .pdf, \
$(addprefix overlaid_zeimena_visvalingam_,$(CROSSING_TOLERANCES)) \
$(addprefix overlaid_sinewave2_douglas_,$(SINEWAVE_TOLERANCES)) \
$(addprefix overlaid_sinewave2_visvalingam_,$(SINEWAVE_TOLERANCES)))
+GEN3 = $(addsuffix .pdf, \
+ $(addprefix overlaid_chaikin_zeimena_douglas_,$(CHAIKIN_CROSSING_TOLERANCES)) \
+ $(addprefix overlaid_chaikin_zeimena_visvalingam_,$(CHAIKIN_CROSSING_TOLERANCES)))
.PHONY: all
all: mj-referatas.pdf mj-prezentacija.pdf
mj-referatas.pdf: mj-referatas.tex version.tex bib.bib zeimena.pdf \
- sinewave1.pdf sinewave2.pdf crossing.pdf $(GEN1) $(GEN2)
+ sinewave1.pdf sinewave2.pdf crossing.pdf $(GEN1) $(GEN2) $(GEN3)
latexmk -shell-escape -g -pdf $<
mj-prezentacija.pdf: mj-prezentacija.tex ../../misc/Logo_vilniaus_universitetas.png \
@@ -48,6 +52,12 @@ define algo2overlay
overlaid_$(1)_$(2)_%.pdf: layer2img.py db/.faux_$(1)_$(2)_%
./layer2img.py $(3) --group1-table=$(1) --group2-table=$(1)_$(2)_$$* \
--outfile $$@
+chaikin_overlaid_$(1)_$(2)_$(3)_%.pdf: layer2img.py db/.chaikin_$(1)_$(2)_%
+ ./layer2img.py $(3) \
+ --group1-table=$(1) \
+ --group2-table=$(1)_$(2)_$$* \
+ --group3-table=chaikin_$(1)_$(2)_$$* \
+ --outfile $$@
endef
define gpkg2pdf
$(1): $(2) ./layer2img.py
diff --git a/II/Referatas/bib.bib b/II/Referatas/bib.bib
@@ -139,3 +139,14 @@
year={1991},
publisher={Longman Scientific \& Technical London}
}
+
+@article{chaikin1974algorithm,
+ title={An algorithm for high-speed curve generation},
+ author={Chaikin, George Merrill},
+ journal={Computer graphics and image processing},
+ volume={3},
+ number={4},
+ pages={346--349},
+ year={1974},
+ publisher={Elsevier}
+}
diff --git a/II/Referatas/chaikin.sql b/II/Referatas/chaikin.sql
@@ -0,0 +1,13 @@
+DROP TABLE IF EXISTS :tbl;
+
+CREATE TABLE :tbl (
+ fid serial NOT NULL,
+ geom geometry(MULTILINESTRING, 3346)
+);
+
+INSERT INTO :tbl (geom) (
+ SELECT
+ ST_ChaikinSmoothing (geom, 3) AS geoms
+ FROM
+ :src);
+
diff --git a/II/Referatas/mj-referatas.tex b/II/Referatas/mj-referatas.tex
@@ -148,8 +148,14 @@ are often used for line generalization:
\item \cite{visvalingam1993line} via
\href{https://postgis.net/docs/ST_SimplifyVW.html}{PostGIS SimplifyVW}.
+
\end{itemize}
+Since both algorithms produce jaggy output lines, it is worthwhile to process
+those through a widely available \cite{chaikin1974algorithm} smoothing
+algorithm via \href{https://postgis.net/docs/ST_ChaikinSmoothing.html}{PostGIS
+ChaikinSmoothing}.
+
Review of the available algorithms will be followed by desiderata for a
possible open-source addition. In the end, we will issue a recommendation,
which algorithm can be picked up and implemented by an avid GIS developer.
@@ -251,10 +257,10 @@ a large circle, ilustrated in figure~\ref{fig:blunt-bent}.
\label{fig:blunt-bent}
\end{figure}
-Once zoomed in to the river crossing area with {\DP} and {\VW} applied, it becomes apparent that both large
-blunts are normalized to single lines, the shape becomes jagged and unpleasant
-for the eye. See table~\ref{tab:comparison-crossing} on
-page~\pageref{tab:comparison-crossing}.
+Once zoomed in to the river crossing area with {\DP} and {\VW} applied, it
+becomes apparent that both large blunts are normalized to single lines, the
+shape becomes jagged and unpleasant for the eye. See
+table~\ref{tab:comparison-crossing} on page~\pageref{tab:comparison-crossing}.
\begin{figure}[h]
\renewcommand{\tabularxcolumn}[1]{>{\center\small}m{#1}}
@@ -280,6 +286,31 @@ page~\pageref{tab:comparison-crossing}.
\label{tab:comparison-crossing}
\end{figure}
+As the reader may observe, the output lines, especially with higher tolerances,
+are jaggy. Higher-tolerance jaggy outputs from {\VW} and {\DP}, passed through Chaikin,
+are displayed in table~\ref{tab:chaikin-crossing} on
+page~\page{tab:chaikin-crossing}.
+
+\begin{figure}[h]
+ \renewcommand{\tabularxcolumn}[1]{>{\center\small}m{#1}}
+ \begin{tabularx}{\textwidth}{ p{2.1cm} | X | X | }
+ Tolerance DP/VW &
+ Douglas \& Peucker &
+ Visvalingam-Whyatt \tabularnewline \hline
+
+ 128/16384 &
+ \includegraphics[width=\linewidth]{chaikin_overlaid_zeimena_douglas_128} &
+ \includegraphics[width=\linewidth]{chaikin_overlaid_zeimena_visvalingam_128} \tabularnewline \hline
+
+ 256/65536 &
+ \includegraphics[width=\linewidth]{chaikin_overlaid_zeimena_douglas_256} &
+ \includegraphics[width=\linewidth]{chaikin_overlaid_zeimena_visvalingam_256} \tabularnewline \hline
+
+ \end{tabularx}
+ \caption{Chaikin-smoothened {\DP} and {\VW} on river crossing area}
+ \label{tab:chaikin-crossing}
+\end{figure}
+
There is another issue on the wishlist beyond jaggyness and loss of large bents
-- combining close bends to larger ones.
