diff --git a/utils/captcha/captcha.go b/utils/captcha/captcha.go
index 14c6c3b3..3616cc7e 100644
--- a/utils/captcha/captcha.go
+++ b/utils/captcha/captcha.go
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Package captcha implements generation and verification of image CAPTCHAs.
 // an example for use captcha
 //
 // ```
@@ -78,7 +79,7 @@ const (
 	// default captcha attributes
 	challengeNums    = 6
 	expiration       = 600
-	fieldIdName      = "captcha_id"
+	fieldIDName      = "captcha_id"
 	fieldCaptchaName = "captcha"
 	cachePrefix      = "captcha_"
 	defaultURLPrefix = "/captcha/"
@@ -93,7 +94,7 @@ type Captcha struct {
 	URLPrefix string
 
 	// specify captcha id input field name
-	FieldIdName string
+	FieldIDName string
 	// specify captcha result input field name
 	FieldCaptchaName string
 
@@ -121,7 +122,7 @@ func (c *Captcha) genRandChars() []byte {
 	return utils.RandomCreateBytes(c.ChallengeNums, defaultChars...)
 }
 
-// beego filter handler for serve captcha image
+// Handler beego filter handler for serve captcha image
 func (c *Captcha) Handler(ctx *context.Context) {
 	var chars []byte
 
@@ -156,8 +157,8 @@ func (c *Captcha) Handler(ctx *context.Context) {
 	}
 }
 
-// tempalte func for output html
-func (c *Captcha) CreateCaptchaHtml() template.HTML {
+// CreateCaptchaHTML tempalte func for output html
+func (c *Captcha) CreateCaptchaHTML() template.HTML {
 	value, err := c.CreateCaptcha()
 	if err != nil {
 		beego.Error("Create Captcha Error:", err)
@@ -168,10 +169,10 @@ func (c *Captcha) CreateCaptchaHtml() template.HTML {
 	return template.HTML(fmt.Sprintf(`<input type="hidden" name="%s" value="%s">`+
 		`<a class="captcha" href="javascript:">`+
 		`<img onclick="this.src=('%s%s.png?reload='+(new Date()).getTime())" class="captcha-img" src="%s%s.png">`+
-		`</a>`, c.FieldIdName, value, c.URLPrefix, value, c.URLPrefix, value))
+		`</a>`, c.FieldIDName, value, c.URLPrefix, value, c.URLPrefix, value))
 }
 
-// create a new captcha id
+// CreateCaptcha create a new captcha id
 func (c *Captcha) CreateCaptcha() (string, error) {
 	// generate captcha id
 	id := string(utils.RandomCreateBytes(15))
@@ -187,13 +188,13 @@ func (c *Captcha) CreateCaptcha() (string, error) {
 	return id, nil
 }
 
-// verify from a request
+// VerifyReq verify from a request
 func (c *Captcha) VerifyReq(req *http.Request) bool {
 	req.ParseForm()
-	return c.Verify(req.Form.Get(c.FieldIdName), req.Form.Get(c.FieldCaptchaName))
+	return c.Verify(req.Form.Get(c.FieldIDName), req.Form.Get(c.FieldCaptchaName))
 }
 
-// direct verify id and challenge string
+// Verify direct verify id and challenge string
 func (c *Captcha) Verify(id string, challenge string) (success bool) {
 	if len(challenge) == 0 || len(id) == 0 {
 		return
@@ -227,11 +228,11 @@ func (c *Captcha) Verify(id string, challenge string) (success bool) {
 	return true
 }
 
-// create a new captcha.Captcha
+// NewCaptcha create a new captcha.Captcha
 func NewCaptcha(urlPrefix string, store cache.Cache) *Captcha {
 	cpt := &Captcha{}
 	cpt.store = store
-	cpt.FieldIdName = fieldIdName
+	cpt.FieldIDName = fieldIDName
 	cpt.FieldCaptchaName = fieldCaptchaName
 	cpt.ChallengeNums = challengeNums
 	cpt.Expiration = expiration
@@ -252,7 +253,7 @@ func NewCaptcha(urlPrefix string, store cache.Cache) *Captcha {
 	return cpt
 }
 
-// create a new captcha.Captcha and auto AddFilter for serve captacha image
+// NewWithFilter create a new captcha.Captcha and auto AddFilter for serve captacha image
 // and add a tempalte func for output html
 func NewWithFilter(urlPrefix string, store cache.Cache) *Captcha {
 	cpt := NewCaptcha(urlPrefix, store)
@@ -261,7 +262,7 @@ func NewWithFilter(urlPrefix string, store cache.Cache) *Captcha {
 	beego.InsertFilter(cpt.URLPrefix+"*", beego.BeforeRouter, cpt.Handler)
 
 	// add to template func map
-	beego.AddFuncMap("create_captcha", cpt.CreateCaptchaHtml)
+	beego.AddFuncMap("create_captcha", cpt.CreateCaptchaHTML())
 
 	return cpt
 }
diff --git a/utils/captcha/image.go b/utils/captcha/image.go
index 8e9039d0..1057192a 100644
--- a/utils/captcha/image.go
+++ b/utils/captcha/image.go
@@ -240,6 +240,7 @@ var font = [][]byte{
 	},
 }
 
+// Image struct
 type Image struct {
 	*image.Paletted
 	numWidth  int