more cleanup

- Added script to generate the diagrams.
- Fixed various things in the maps.

Author: sckoehler

README.md

@@ -5,12 +5,12 @@ scalar vector graphics (SVG) format.  My original intent was to
 generate diagrams showing the location of the Herschel 400 objects on
 the Sky Atlas 2000 maps, something like the following:
 
-<img src="images/h400_22.svg" width="300">
+<img src="images/h400_9.svg">
 
 After discovering Diego Hernangomez's excellent repository of
 [celestial data](https://dieghernan.github.io/celestial_data/data) in
 geojson format, I expanded the tool to add more and more information
 layers.  The end result looks like this:
 
-<img src="images/map22.svg">
+<img src="images/map9.svg">
 

genmap

@@ -68,6 +68,13 @@ DSO_STROKE = 0.5
 # Utility functions
 ###########################################################################
 
+def parse_width(w)
+  # Parse a width specification into its numeric part and its units, if any
+  m = /^([\d.]+)(.*)$/.match(w)
+  abort "Width expression should be <num><units>" unless m
+  [m[1].to_f, m[2]]
+end
+
 def g(x)
   # Convert a floating point number to a string, limiting the digits.
   "%.2f" % x
@@ -88,9 +95,11 @@ def deg_to_rad(dec)
   dec * Math::PI/180
 end
 
-def project(ra, dec, phi1, phi2, ra0, dec0)
+def project(ra, dec, phi1, phi2, ra0, dec0, scale=Scale)
   # Project ra, dec onto a flat map using standard parallels phi1 and phi2
-  # and centered on ra0, dec0.  All parameters are in radians.
+  # and centered on ra0, dec0.  All parameters are in radians. The
+  # returned x and y are scaled so that the map is 700 pixels wide. This
+  # makes it easier to keep the line strokes an appropriate width.
 
   # Normalize the cone/cylinder opposite ra0
   ra += 2*Math::PI if ra0-ra > Math::PI
@@ -110,7 +119,7 @@ def project(ra, dec, phi1, phi2, ra0, dec0)
     x = rho*Math.sin(theta)
     y = rho0 - rho*Math.cos(theta)
   end
-  return Scale*x, -Scale*y
+  return scale*x, -scale*y
 end
 
 def parse_coord(coord)
@@ -250,7 +259,7 @@ end
 def draw_border_path(pts)
   # Draw a constellation border path.
   puts %Q[<polyline points="#{pts.map{|x| x.map{|y| g(y)}.join(",")}.join(" ")}"
-          style="fill:none;stroke:grey;stroke-width:0.5;stroke-dasharray:3"/>]
+          style="fill:none;stroke:grey;stroke-width:0.5"/>]
 end
 
 def draw_grid_path(pts)
@@ -385,7 +394,7 @@ end
 def plot_border(bounds)
   # Print the map border.
   xmin, xmax, ymin, ymax = bounds
-  puts %Q[<rect x=#{f(xmin)} y=#{f(ymin)} width=#{f(xmax-xmin)} height=#{f(ymax-ymin)} stroke="black" stroke-width="1" fill="none"/>]
+  puts %Q[<rect x=#{f(xmin)} y=#{f(ymin)} width=#{f(xmax-xmin)} height=#{f(ymax-ymin)} stroke="black" stroke-width="0.5" fill="none"/>]
 end
 
 def plot_map_number(bounds, map_number)
@@ -402,8 +411,8 @@ options = {}
 OptionParser.new do |opts|
   opts.banner = "Usage: test.rb [options]"
 
-  opts.on("-a", "--scale FACTOR", Integer, "Scale factor") do |v|
-    options[:scale] = v
+  opts.on("-w", "--width ", String, "Width of image") do |v|
+    options[:width] = v
   end
   opts.on("-r", "--margin PIXELS", Integer, "Margin outside map") do |v|
     options[:margin] = v
@@ -417,7 +426,7 @@ OptionParser.new do |opts|
   opts.on("-l", "--lr DDDD.D+DDDD", String, "Lower-right coordinate") do |v|
     options[:lr] = v
   end
-  opts.on("-s", "--stars MAG", Float, "Plot stars") do |v|
+  opts.on("-S", "--stars MAG", Float, "Plot stars") do |v|
     options[:stars] = v
   end
   opts.on("-g", "--grid", "Plot grid") do |v|
@@ -435,20 +444,18 @@ OptionParser.new do |opts|
   opts.on("-D", "--dso MAG", Float, "Plot deep sky objects") do |v|
     options[:dso] = v
   end
-  opts.on("-c", "--const", "Plot constellation lines") do |v|
+  opts.on("-C", "--const", "Plot constellation lines") do |v|
     options[:const] = v
   end
-  opts.on("-b", "--border", "Plot constellation borders") do |v|
+  opts.on("-B", "--border", "Plot constellation borders") do |v|
     options[:border] = v
   end
-  opts.on("-w", "--milkyway", "Plot milky way contours") do |v|
+  opts.on("-W", "--milkyway", "Plot milky way contours") do |v|
     options[:milkyway] = v
   end
 end.parse!
 
-# Fixme: we need a different solution than scale
-Scale = options[:scale] || 700
-
+Width = options[:width] || "6in"
 Margin = options[:margin] || 0
 
 # Establish some globals to specify the map to be generated.
@@ -474,17 +481,22 @@ else
 
   # Approximate the map center.
   Ra0 = (Ra1+Ra2)/2
-  Ra0_ha = (ra1+ra2)/2
+  Ra0_ha = Ra0*24/(2*Math::PI)
   Dec0 = (Dec1+Dec2)/2
 end
 
 # Determine the coordinates of the map boundary.
+xmin, ymin = project(Ra1, Dec1, Phi1, Phi2, Ra0, Dec0, 1.0)
+xmax, ymax = project(Ra2, Dec2, Phi1, Phi2, Ra0, Dec0, 1.0)
+Scale = 700.0/(xmax-xmin)
 xmin, ymin = project(Ra1, Dec1, Phi1, Phi2, Ra0, Dec0)
 xmax, ymax = project(Ra2, Dec2, Phi1, Phi2, Ra0, Dec0)
 bounds = [xmin, xmax, ymin, ymax]
+amt, units = parse_width(Width)
+Height = (amt*(ymax-ymin)/(xmax-xmin)).to_s + units
 
 # Print the header material.
-puts %Q[<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 #{g(xmax-xmin+2*Margin)} #{g(ymax-ymin+2*Margin)}">]
+puts %Q[<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 #{g(xmax-xmin+2*Margin)} #{g(ymax-ymin+2*Margin)}" width="#{Width}" height="#{Height}">]
 puts %Q[<g transform="translate(#{g(-xmin+Margin)}, #{g(-ymin+Margin)})">]
 puts %Q[<clipPath id="CP">]
 puts %Q[<rect x=#{f(xmin)} y=#{f(ymin)} width=#{f(xmax-xmin)} height=#{f(ymax-ymin)} stroke="black" stroke-width="1" fill="white"/>]

images/h400_22.svg

@@ -0,0 +1,4 @@
+#
+
+./genmap -m 9 -w 6in -S 7 -B -H -C -W > images/map9.svg
+./genmap -m 9 -w 3in -H -p > images/h400_9.svg

images/h400_9.svg

@@ -0,0 +1,4 @@
+#
+
+../genmap -m 9 -w 6in -S 7 -B -H -C -W > images/map9.svg
+../genmap -m 9 -w 3in -H -p > h400_9.svg