addressing color palette issue in issue red-data-tools#34

example/issue34.rb

@@ -0,0 +1,39 @@
+#!/bin/env ruby
+
+$LOAD_PATH << "#{__dir__}/../lib"
+require "unicode_plot"
+
+#
+# Example of using the 256 color pallette
+#
+
+# dummy plot-line to set canvas
+plt = UnicodePlot.lineplot([0,0],[0,0], title: "256-color", color: 0,
+                           xlim: [0,31], ylim: [0,31],
+                           width: 33, height: 32, canvas: :braille)
+# sweep some colored lines using 256 color palette
+(0..255).each do |colornum|
+  x1 = (colornum / 32).floor * 4
+  x2 = x1 + 3
+  y = colornum % 32
+  UnicodePlot.lineplot!(plt, [x1, x2],[y, y], color: colornum)
+end
+plt.render
+
+#
+# Example of using standard 8-color pallete with line-plots and named colors
+# When lines cross over each other, some 'mixing' effect happens that will
+# blend colors by OR'ing their value.
+#
+# Noting that 16-color cannot be accessed with line-plot, as
+# the ':light_*' colors and ':black' are not accepted.
+
+colorlist = %i[ normal red green yellow blue magenta cyan white ]
+plt = UnicodePlot.lineplot([0,0],[0,0], title: "8-color-mixing", color: 0,
+                           xlim: [0,15], ylim: [0,15],
+                           width: 33, height: 16, canvas: :braille)
+colorlist.each_with_index do |color, y|
+  UnicodePlot.lineplot!(plt, [0, 15],[y*2, y*2], color: color)
+  UnicodePlot.lineplot!(plt, [y*2, y*2],[0, 15],  color: color)
+end
+plt.render

lib/unicode_plot/braille_canvas.rb

@@ -46,7 +46,7 @@ def pixel!(pixel_x, pixel_y, color)
       index = index_at(char_x - 1, char_y - 1)
       if index
         @grid[index] = (@grid[index].ord | BRAILLE_SIGNS[char_x_off - 1][char_y_off - 1]).chr(Encoding::UTF_8)
-        @colors[index] |= COLOR_ENCODE[color]
+        @colors[index] |= COLOR_ENCODE.fetch(color, color)
       end
       color
     end

lib/unicode_plot/lookup_canvas.rb

@@ -29,7 +29,7 @@ def pixel!(pixel_x, pixel_y, color)
       index = index_at(char_x - 1, char_y - 1)
       if index
         @grid[index] |= lookup_encode(char_x_off - 1, char_y_off - 1)
-        @colors[index] |= COLOR_ENCODE[color]
+        @colors[index] |= COLOR_ENCODE.fetch(color, color)
       end
     end
 

lib/unicode_plot/styled_printer.rb

@@ -80,7 +80,7 @@ def print_styled(out, *args, bold: false, color: :normal)
     end
 
     def print_color(out, color, *args)
-      color = COLOR_DECODE[color]
+      color = COLOR_DECODE.fetch(color, color)
       print_styled(out, *args, color: color)
     end