Created Colorized barcode (markdown)

Colorized-barcode.md

@@ -0,0 +1,43 @@
+To colorize a barcode you could use the following code:
+
+```golang
+package main
+
+import (
+    "github.com/boombuler/barcode"
+    "github.com/boombuler/barcode/qr"
+    "image/color"
+    "image/png"
+    "os"
+)
+
+type coloredBarcode struct {
+    barcode.Barcode
+    cm color.Model
+    fg color.Color
+    bg color.Color
+}
+
+func NewColoredBarcode(bc barcode.Barcode, cm color.Model, foreground color.Color, background color.Color) barcode.Barcode {
+    return &coloredBarcode{bc, cm, foreground, background}
+}
+func (bc *coloredBarcode) ColorModel() color.Model {
+    return bc.cm
+}
+func (bc *coloredBarcode) At(x, y int) color.Color {
+    c := bc.Barcode.At(x, y)
+    if c == color.Black {
+        return bc.fg
+    } else {
+        return bc.bg
+    }
+}
+
+func main() {
+    bc, _ := qr.Encode("foobar", qr.L, qr.Auto)
+    bc = NewColoredBarcode(bc, color.RGBAModel, color.RGBA{255, 0, 0, 255}, color.RGBA{255, 255, 0, 255})
+    f, _ := os.Create("foobar.png")
+    defer f.Close()
+    png.Encode(f, bc)
+}
+```