add: LoadFont API

captcha.go

@@ -78,6 +78,13 @@ func init() {
 	}
 }
 
+// LoadFont let you load an external font
+func LoadFont(fontData []byte) error {
+	var err error
+	ttfFont, err = freetype.ParseFont(fontData)
+	return err
+}
+
 // New creates a new captcha.
 // It returns captcha data and any freetype drawing error encountered
 func New(width int, height int, option ...SetOption) (*Data, error) {

captcha_test.go

@@ -2,6 +2,7 @@ package captcha
 
 import (
 	"bytes"
+	"golang.org/x/image/font/gofont/goregular"
 	"image/color"
 	"testing"
 )
@@ -36,3 +37,15 @@ func TestCovNilFontError(t *testing.T) {
 
 	ttfFont = temp
 }
+
+func TestLoadFont(t *testing.T) {
+	err := LoadFont(goregular.TTF)
+	if err != nil {
+		t.Fatal("Fail to load go font")
+	}
+
+	err = LoadFont([]byte("invalid"))
+	if err == nil {
+		t.Fatal("LoadFont incorrecly parse an invalid font")
+	}
+}