standardize Rubyplot coordinate system and allow changes on a per Figure basis

Author: v0dro

CONTRIBUTING.md

@@ -4,8 +4,8 @@
 
 Rubyplot assumes that the co-ordinate system has the origin at the bottom left corner
 of the graph. This helps in keeping all pixel co-ordinates positive values. The bottom
-left corner is `(Rubyplot::MIN_X, Rubyplot::MIN_X)` and the upper left corner is 
-`(Rubyplot::MAX_X, Rubyplot::MAX_Y)`. The backend should be accomodated to work with 
+left corner is `(Rubyplot.min_x, Rubyplot.min_x)` and the upper left corner is 
+`(Rubyplot::max_x, Rubyplot.max_y)`. The backend should be accomodated to work with 
 this system. They are also denoted as and . This system is known as the 
 `Rubyplot Artist Co-ordinates` system internally within the codebase.
 
@@ -72,6 +72,8 @@ in human-understadable format and uses the appropriate GR primitives to do its j
 
 GR does not allow changing the internal DPI setting as of now (which is 600).
 The size of the figure can be set using the `setwsviewport` or `setwswindow` functions.
+Therefore, `setwsviewport(0, 6 * 0.0254, 0, 3 * 0.0254)` would create a 6 by 3
+inch image at 600 dpi.
 
 ## setwindow and setviewport
 

lib/rubyplot.rb

@@ -124,14 +124,7 @@ module Rubyplot
     :hatch
   ].freeze
 
-  # Min. co-ordinates of the lower left corner.
-  MIN_X = 0
-  MIN_Y = 0
-
-  # Max. co-ordinates of the upper right corner.
-  MAX_X = 100
-  MAX_Y = 100
-  class << self
+  class << self    
     def backend
       @backend
     end
@@ -146,3 +139,4 @@ def set_backend b
     end
   end
 end # module Rubyplot
+

lib/rubyplot/artist/axes.rb

@@ -38,9 +38,9 @@ class Axes < Base
       attr_accessor :abs_x
       # Y co-ordinate of lower left corner of this Axes.
       attr_accessor :abs_y
-      # Width of this Axes object. Between Rubyplot::MIN_X and MAX_X.
+      # Width of this Axes object. Between Rubyplot.min_x and max_x.
       attr_accessor :width
-      # Height of this Axes object. Between Rubyplot::MIN_Y and MAX_Y.
+      # Height of this Axes object. Between Rubyplot.min_y and MAX_Y.
       attr_accessor :height
 
       # @param figure [Rubyplot::Figure] Figure object to which this Axes belongs.

lib/rubyplot/artist/figure.rb

@@ -1,8 +1,8 @@
 module Rubyplot
   module Artist
     class Figure < Artist::Base
-      DEFAULT_TARGET_WIDTH = 800
-
+      DEFAULT_CANVAS_DIM = 40.0
+      
       # Title on the figure.
       attr_reader :title
       # Number of Axes objects in the rows.
@@ -29,23 +29,31 @@ class Figure < Artist::Base
       attr_reader :marker_color
       # Font color specified as a Symbol from Rubyplot::COLOR::COLOR_INDEX.
       attr_reader :font_color
+      # Unit of the figure size.
+      attr_reader :figsize_unit
+      attr_reader :max_x
+      attr_reader :max_y
+      attr_reader :min_x
+      attr_reader :min_y
 
       # Initialize a Rubyplot::Artist::Figure object.
       # @param height [Integer] nil Height in pixels of the complete Figure.
       # @param width [Integer] nil Width in pixels of the complete Figure.
-      def initialize(height: nil, width: nil)
+      def initialize(height: nil, width: nil, figsize_unit: :cm)
         super(0, 0)
         @title = ''
         @nrows = 1
         @ncols = 1
-        @width = width || DEFAULT_TARGET_WIDTH
-        @height = height || @width * 0.75
+        @width = (width || DEFAULT_CANVAS_DIM).to_f
+        @height = (height || DEFAULT_CANVAS_DIM).to_f
         @top_spacing = 5
         @bottom_spacing = 5
         @left_spacing = 5
         @right_spacing = 5
         @subplots = nil
         @n = 0
+        @figsize_unit = figsize_unit
+        set_rubyplot_artist_coords!
         setup_default_theme
         add_subplots! @nrows, @ncols
       end
@@ -68,12 +76,12 @@ def add_subplots!(nrows, ncols)
       # @param ncol [Integer] Y co-ordinate of the subplot.
       def add_subplot!(nrow, ncol)
         # FIXME: make this work for mutliple subplots.
-        plottable_width = Rubyplot::MAX_X - (@left_spacing + @right_spacing)
-        plottable_length = Rubyplot::MAX_Y - (@top_spacing + @bottom_spacing)
+        plottable_width = (@max_x - (@left_spacing + @right_spacing)).to_f
+        plottable_length = (@max_y - (@top_spacing + @bottom_spacing)).to_f
         @subplots[nrow][ncol] = Rubyplot::Artist::Axes.new(
           self,
-          abs_x: @left_spacing + (plottable_width.to_f / @ncols) * ncol,
-          abs_y: @bottom_spacing + (plottable_length.to_f / @nrows) * nrow,
+          abs_x: @left_spacing + (plottable_width / @ncols) * ncol,
+          abs_y: @bottom_spacing + (plottable_length / @nrows) * nrow,
           width: plottable_width / @ncols,
           height: plottable_length / @nrows
         )
@@ -106,6 +114,20 @@ def write(file_name, device: :file)
 
       private
 
+      def set_rubyplot_artist_coords!
+        @max_x = 100.0
+        @max_y = 100.0
+        @min_x = 0.0
+        @min_y = 0.0
+        if @height > @width
+          aspect_ratio = @height / @width
+          @max_y = @max_y * aspect_ratio
+        elsif @height < @width
+          aspect_ratio = @width / @height
+          @max_x = @max_x * aspect_ratio
+        end
+      end
+
       def setup_default_theme
         defaults = {
           marker_color: :white,

lib/rubyplot/backend/gr_wrapper.rb

@@ -147,8 +147,14 @@ class GRWrapper < Base
       def initialize
         @axes_map = {} # Mapping between viewports and their respective Axes.
         @file_name = nil
-        @xspread = Rubyplot::MAX_X.abs + Rubyplot::MIN_X.abs
-        @yspread = Rubyplot::MAX_Y.abs + Rubyplot::MIN_Y.abs
+      end
+
+      def xspread
+        (@figure.max_x.abs + @figure.min_x.abs).to_f
+      end
+
+      def yspread
+        (@figure.max_y.abs + @figure.min_y.abs).to_f
       end
 
       # Draw X axis for the currently selected Axes.
@@ -348,17 +354,17 @@ def to_rgb color
 
       # Transform a X quantity to Normalized Device Co-ordinates.
       def transform_x_ndc coord
-        coord.to_f / @xspread
+        coord.to_f / xspread
       end
 
       # Transform a Y quantity to Normalized Device Co-ordinates.
       def transform_y_ndc coord
-        coord.to_f / @yspread
+        coord.to_f / yspread
       end
 
       # Transform a quanitity that represents neither X nor Y co-ordinate into NDC.
       def transform_avg_ndc coord
-        coord / ((@xspread + @yspread) / 2)
+        coord / ((xspread + yspread) / 2)
       end
 
       # Set the window on the canvas within which the plotting will take place
@@ -368,13 +374,13 @@ def within_window(abs=false, &block)
           GR.setviewport(0,1,0,1)
           GR.setwindow(0,1,0,1)
         else
-          vp_min_x = (@active_axes.abs_x + @active_axes.left_margin) / @xspread
-          vp_min_y = (@active_axes.abs_y + @active_axes.bottom_margin) / @yspread
+          vp_min_x = (@active_axes.abs_x + @active_axes.left_margin) / xspread
+          vp_min_y = (@active_axes.abs_y + @active_axes.bottom_margin) / yspread
           vp_max_x = (@active_axes.abs_x + @active_axes.width -
-            @active_axes.right_margin) / @xspread
+            @active_axes.right_margin) / xspread
           vp_max_y = (@active_axes.abs_y + @active_axes.height -
-            @active_axes.top_margin) / @yspread
-          
+            @active_axes.top_margin) / yspread
+
           GR.setviewport(vp_min_x, vp_max_x, vp_min_y, vp_max_y)
           GR.setwindow(
             @active_axes.x_range[0],

lib/rubyplot/backend/magick_wrapper.rb

@@ -166,11 +166,11 @@ def render_gradient(top_color, bottom_color, width, height, direct)
 
       # Transform X co-ordinate.
       def transform_x x
-        (@canvas_width * x) / Rubyplot::MAX_X
+        (@canvas_width * x) / Rubyplot.max_x
       end
 
       def transform_y y
-        (@canvas_height * (Rubyplot::MAX_Y - y)) / Rubyplot::MAX_Y
+        (@canvas_height * (Rubyplot.max_y - y)) / Rubyplot.max_y
       end
 
       # Transform quantity that depends on X and Y.

spec/axes_spec.rb

@@ -303,7 +303,7 @@
       axes.x_ticks = [ '5/6', '5/15', '5/24', '5/36' ]
     end
 
-    it "adds multiple bar plots for wide graph" do
+    it "adds multiple bar plots for wide graph", focus: true do
       @figure = Rubyplot::Figure.new(height: 400, width: 800)
       axes = @figure.add_subplot! 0,0
       @planet_data.each do |name, nums|
@@ -387,7 +387,7 @@
     end
 
     it "adds a simple scatter plot." do
-      @figure = Rubyplot::Figure.new 
+      @figure = Rubyplot::Figure.new
       axes = @figure.add_subplot! 0,0
       axes.scatter! do |p|
         p.data @x1, @y1

spec/figure_spec.rb

@@ -2,12 +2,15 @@
 
 describe Rubyplot::Figure do
   context ".new" do
-    it "accepts figsize in centimeter (default)", focus: true do
+    it "accepts figsize in centimeter (default)" do
       fig = Rubyplot::Figure.new(width: 30, height: 40)
 
       expect(fig.width).to eq(30)
       expect(fig.height).to eq(40)
       expect(fig.figsize_unit).to eq(:cm)
+
+      expect(fig.max_x).to eq(100.0)
+      expect(fig.max_y).to be_within(0.01).of(133.33)
     end
 
     it "accepts figsize in pixels" do
@@ -37,18 +40,18 @@
     it "changes Rubyplot Artist Co-ordinates as per aspect ratio." do
       fig = Rubyplot::Figure.new(width: 20, height: 20)
 
-      expect(Rubyplot.max_x).to eq(100.0)
-      expect(Rubyplot.max_y).to eq(100.0)
+      expect(fig.max_x).to eq(100.0)
+      expect(fig.max_y).to eq(100.0)
 
       fig = Rubyplot::Figure.new(width: 30, height: 20)
 
-      expect(Rubyplot.max_x).to eq(150.0)
-      expect(Rubyplot.max_y).to eq(100.0)
+      expect(fig.max_x).to eq(150.0)
+      expect(fig.max_y).to eq(100.0)
 
       fig = Rubyplot::Figure.new(width: 20, height: 30)
 
-      expect(Rubyplot.max_x).to eq(100.0)
-      expect(Rubyplot.max_y).to eq(150.0)
+      expect(fig.max_x).to eq(100.0)
+      expect(fig.max_y).to eq(150.0)
     end
   end