Add example HTTP server that uses the package.

.gitignore

@@ -28,3 +28,4 @@ capgen/*.wav
 # Programs
 capgen/capgen
 generate/generate
+example/example

example/Makefile

@@ -0,0 +1,7 @@
+include $(GOROOT)/src/Make.inc
+
+TARG=example
+GOFILES=\
+	main.go
+
+include $(GOROOT)/src/Make.cmd

example/main.go

@@ -0,0 +1,48 @@
+// example of HTTP server that uses the captcha package.
+package main
+
+import (
+	"fmt"
+	"github.com/dchest/captcha"
+	"http"
+	"template"
+)
+
+var formTemplate = template.MustParse(formTemplateSrc, nil)
+
+func showFormHandler(w http.ResponseWriter, r *http.Request) {
+	d := struct{ CaptchaId string }{captcha.New(captcha.StdLength)}
+	if err := formTemplate.Execute(w, &d); err != nil {
+		http.Error(w, err.String(), http.StatusInternalServerError)
+	}
+}
+
+func processFormHandler(w http.ResponseWriter, r *http.Request) {
+	if !captcha.VerifyString(r.FormValue("captchaId"), r.FormValue("captchaSolution")) {
+		fmt.Fprintf(w, "Wrong captcha solution! No robots allowed!")
+		return
+	}
+	fmt.Fprintf(w, "Great job, human! You solved the captcha.")
+}
+
+func main() {
+	http.HandleFunc("/", showFormHandler)
+	http.HandleFunc("/process", processFormHandler)
+	http.Handle("/captcha/", captcha.Server(captcha.StdWidth, captcha.StdHeight))
+	http.ListenAndServe(":8080", nil)
+}
+
+const formTemplateSrc = `
+<form action="/process" method=post>
+<p>Type the numbers you see in the picture below:</p>
+<p><img src="/captcha/{CaptchaId}.png" alt="Captcha image"></p>
+<a href="#" onclick="var e=getElementById('audio'); e.display=true; e.play(); return false">Play Audio</a>
+<audio id=audio controls style="display:none">
+  <source src="/captcha/{CaptchaId}.wav" type="audio/x-wav">
+  You browser doesn't support audio.
+  <a href="/captcha/{CaptchaId}.wav?get">Download file</a> to play it in the external player.
+</audio>
+<input type=hidden name=captchaId value={CaptchaId}><br>
+<input name=captchaSolution>
+<input type=submit>
+`