Build a color chart.

bin/__build_sgr_code

@@ -100,6 +100,77 @@ function dump_colors()
     exit 0
 }
 
+function cube_row()
+{
+	r_base=${1}
+	g=0
+	while (( g < 6 ))
+	do
+		u=0
+		while (( u < 3 ))
+		do
+			r=$(( r_base + u ))
+
+			b=0
+			while (( b < 6 ))
+			do
+				i=$(( 16 + ( r * 36 ) + ( g * 6 ) + ( b ) ))
+
+				txt="" && [ ${g} -lt 3 ] && txt=';37;1'
+
+				printf "[30${txt}m[48;5;${i}m%3i " ${i}
+
+				b=$(( b + 1 ))
+			done
+
+			printf '  '
+
+			u=$(( u + 1 ))
+		done
+
+		printf '\n'
+
+		g=$(( g + 1 ))
+	done
+	printf '\n'
+}
+
+function greyscale_chart()
+{
+	[ ${i} -ge 244 ] && txt=";30"
+
+	local k=$(( i + 12 ))
+	while (( i < k ))
+	do
+		printf "[48;5;${i};37;1${txt}m%3i " ${i}
+		i=$(( i + 1 ))
+	done
+	printf '\n'
+}
+
+function color_chart()
+{
+	i=0
+
+	# Base 16
+	while (( i < 16 ))
+	do
+		[ ${i} -gt 0 ] && txt=";30"
+
+		printf "[37;1${txt};48;5;${i}m%3i " ${i}
+		i=$(( i + 1 ))
+	done
+	printf '\n\n'
+
+	r=0;g=0;b=0
+	cube_row 0
+	cube_row 3
+	i=$(( 6 * 6 * 6 + 16 ))
+
+	greyscale_chart
+	greyscale_chart
+}
+
 function setup_color_depth()
 {
     use_8_bit=0
@@ -383,6 +454,7 @@ function build_sgr_code()
 {
     case $1 in
         dump-colors) dump_colors ;;
+        color-chart) color_chart ;;
 
         reset) next=0 ;;
         bold) next=1 ;;