add 256 color support

color.go

@@ -156,6 +156,16 @@ func New(value ...Attribute) *Color {
 	return c
 }
 
+// Co256 returns a new foreground color in 256-color mode.
+func Co256(n int) *Color {
+	return New(foreground, 5, Attribute(n))
+}
+
+// BgCo256 returns a new background color in 256-color mode.
+func BgCo256(n int) *Color {
+	return New(background, 5, Attribute(n))
+}
+
 // RGB returns a new foreground color in 24-bit RGB.
 func RGB(r, g, b int) *Color {
 	return New(foreground, 2, Attribute(r), Attribute(g), Attribute(b))
@@ -166,6 +176,18 @@ func BgRGB(r, g, b int) *Color {
 	return New(background, 2, Attribute(r), Attribute(g), Attribute(b))
 }
 
+// AddCo256 is used to chain foreground 256-color SGR parameters.
+func (c *Color) AddCo256(n int) *Color {
+	c.params = append(c.params, foreground, 5, Attribute(n))
+	return c
+}
+
+// AddBgCo256 is used to chain background 256-color SGR parameters.
+func (c *Color) AddBgCo256(n int) *Color {
+	c.params = append(c.params, background, 5, Attribute(n))
+	return c
+}
+
 // AddRGB is used to chain foreground RGB SGR parameters. Use as many as parameters to combine
 // and create custom color objects. Example: .Add(34, 0, 12).Add(255, 128, 0).
 func (c *Color) AddRGB(r, g, b int) *Color {

color_test.go

@@ -10,6 +10,35 @@ import (
 	"github.com/mattn/go-colorable"
 )
 
+func Test256Color(t *testing.T) {
+	rb := new(bytes.Buffer)
+	Output = rb
+	NoColor = false
+	testColors := make([]struct {
+		text string
+		n    int
+	}, 256)
+	for i := 0; i < 256; i++ {
+		testColors[i].text = fmt.Sprintf("%d", i)
+		testColors[i].n = i
+	}
+
+	for _, c := range testColors {
+		New().AddCo256(c.n).Print(c.text)
+
+		line, _ := rb.ReadString('\n')
+		scannedLine := fmt.Sprintf("%q", line)
+		colored := fmt.Sprintf("\x1b[38;5;%dm%s\x1b[0m", c.n, c.text)
+		escapedForm := fmt.Sprintf("%q", colored)
+
+		fmt.Printf("%s\t: %s\n", c.text, line)
+
+		if scannedLine != escapedForm {
+			t.Errorf("Expecting %s, got '%s'\n", escapedForm, scannedLine)
+		}
+	}
+}
+
 // Testing colors is kinda different. First we test for given colors and their
 // escaped formatted results. Next we create some visual tests to be tested.
 // Each visual test includes the color name to be compared.