wip chaikin

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

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}
+}

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);
+

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.