diff --git a/qr/alphanumeric.go b/qr/alphanumeric.go
index 73841c1..749a0fa 100644
--- a/qr/alphanumeric.go
+++ b/qr/alphanumeric.go
@@ -6,11 +6,6 @@ import (
 	"github.com/boombuler/barcode"
 )
 
-type alphaNumericEncoding struct {
-}
-
-var AlphaNumeric Encoding = alphaNumericEncoding{}
-
 var alphaNumericTable map[byte]int = map[byte]int{
 	'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9,
 	'A': 10, 'B': 11, 'C': 12, 'D': 13, 'E': 14, 'F': 15, 'G': 16, 'H': 17, 'I': 18, 'J': 19,
@@ -19,11 +14,7 @@ var alphaNumericTable map[byte]int = map[byte]int{
 	'+': 40, '-': 41, '.': 42, '/': 43, ':': 44,
 }
 
-func (ane alphaNumericEncoding) String() string {
-	return "AlphaNumeric"
-}
-
-func (ane alphaNumericEncoding) encode(content string, ecl ErrorCorrectionLevel) (*barcode.BitList, *versionInfo, error) {
+func encodeAlphaNumeric(content string, ecl ErrorCorrectionLevel) (*barcode.BitList, *versionInfo, error) {
 
 	contentLenIsOdd := len(content)%2 == 1
 	contentBitCount := (len(content) / 2) * 11
@@ -43,14 +34,14 @@ func (ane alphaNumericEncoding) encode(content string, ecl ErrorCorrectionLevel)
 		c1, ok1 := alphaNumericTable[content[idx*2]]
 		c2, ok2 := alphaNumericTable[content[(idx*2)+1]]
 		if !ok1 || !ok2 {
-			return nil, nil, fmt.Errorf("\"%s\" can not be encoded as %s", content, ane)
+			return nil, nil, fmt.Errorf("\"%s\" can not be encoded as %s", content, AlphaNumeric)
 		}
 		res.AddBits(c1*45+c2, 11)
 	}
 	if contentLenIsOdd {
 		c1, ok := alphaNumericTable[content[len(content)-1]]
 		if !ok {
-			return nil, nil, fmt.Errorf("\"%s\" can not be encoded as %s", content, ane)
+			return nil, nil, fmt.Errorf("\"%s\" can not be encoded as %s", content, AlphaNumeric)
 		}
 		res.AddBits(c1, 6)
 	}
diff --git a/qr/alphanumeric_test.go b/qr/alphanumeric_test.go
index aeb9fdb..476c1d6 100644
--- a/qr/alphanumeric_test.go
+++ b/qr/alphanumeric_test.go
@@ -16,25 +16,27 @@ func makeString(length int) string {
 }
 
 func Test_AlphaNumericEncoding(t *testing.T) {
-	x, vi, err := AlphaNumeric.encode("HELLO WORLD", M)
+	encode := AlphaNumeric.getEncoder()
+
+	x, vi, err := encode("HELLO WORLD", M)
 
 	if x == nil || vi == nil || vi.Version != 1 || bytes.Compare(x.GetBytes(), []byte{32, 91, 11, 120, 209, 114, 220, 77, 67, 64, 236, 17, 236, 17, 236, 17}) != 0 {
 		t.Errorf("\"HELLO WORLD\" failed to encode: %s", err)
 	}
 
-	x, vi, err = AlphaNumeric.encode(makeString(4296), L)
+	x, vi, err = encode(makeString(4296), L)
 	if x == nil || vi == nil || err != nil {
 		t.Fail()
 	}
-	x, vi, err = AlphaNumeric.encode(makeString(4297), L)
+	x, vi, err = encode(makeString(4297), L)
 	if x != nil || vi != nil || err == nil {
 		t.Fail()
 	}
-	x, vi, err = AlphaNumeric.encode("ABc", L)
+	x, vi, err = encode("ABc", L)
 	if x != nil || vi != nil || err == nil {
 		t.Fail()
 	}
-	x, vi, err = AlphaNumeric.encode("hello world", M)
+	x, vi, err = encode("hello world", M)
 
 	if x != nil || vi != nil || err == nil {
 		t.Error("\"hello world\" should not be encodable in alphanumeric mode")
diff --git a/qr/automatic.go b/qr/automatic.go
index fec8817..c82bd38 100644
--- a/qr/automatic.go
+++ b/qr/automatic.go
@@ -5,22 +5,12 @@ import (
 	"github.com/boombuler/barcode"
 )
 
-type autoEncoding struct {
-}
-
-// choose the best matching encoding
-var Auto Encoding = autoEncoding{}
-
-func (ne autoEncoding) String() string {
-	return "Auto"
-}
-
-func (ne autoEncoding) encode(content string, ecl ErrorCorrectionLevel) (*barcode.BitList, *versionInfo, error) {
-	bits, vi, _ := Numeric.encode(content, ecl)
+func encodeAuto(content string, ecl ErrorCorrectionLevel) (*barcode.BitList, *versionInfo, error) {
+	bits, vi, _ := Numeric.getEncoder()(content, ecl)
 	if bits != nil && vi != nil {
 		return bits, vi, nil
 	}
-	bits, vi, _ = AlphaNumeric.encode(content, ecl)
+	bits, vi, _ = AlphaNumeric.getEncoder()(content, ecl)
 	if bits != nil && vi != nil {
 		return bits, vi, nil
 	}
diff --git a/qr/automatic_test.go b/qr/automatic_test.go
index 9104a03..850a567 100644
--- a/qr/automatic_test.go
+++ b/qr/automatic_test.go
@@ -6,16 +6,16 @@ import (
 )
 
 func Test_AutomaticEncoding(t *testing.T) {
-	tests := map[string]Encoding{
-		"0123456789":          Numeric,
-		"ALPHA NUMERIC":       AlphaNumeric,
+	tests := map[string]encodeFn{
+		"0123456789":          Numeric.getEncoder(),
+		"ALPHA NUMERIC":       AlphaNumeric.getEncoder(),
 		"no matching encoing": nil,
 	}
 
 	for str, enc := range tests {
-		testValue, _, _ := Auto.encode(str, M)
+		testValue, _, _ := Auto.getEncoder()(str, M)
 		if enc != nil {
-			correctValue, _, _ := enc.encode(str, M)
+			correctValue, _, _ := enc(str, M)
 			if testValue == nil || bytes.Compare(correctValue.GetBytes(), testValue.GetBytes()) != 0 {
 				t.Errorf("wrong encoding used for '%s'", str)
 			}
diff --git a/qr/encoder.go b/qr/encoder.go
index 6ed548b..aaa1b60 100644
--- a/qr/encoder.go
+++ b/qr/encoder.go
@@ -6,13 +6,42 @@ import (
 	"image"
 )
 
-type Encoding interface {
-	fmt.Stringer
-	encode(content string, eccLevel ErrorCorrectionLevel) (*barcode.BitList, *versionInfo, error)
+type encodeFn func(content string, eccLevel ErrorCorrectionLevel) (*barcode.BitList, *versionInfo, error)
+
+type Encoding byte
+
+const (
+	Auto Encoding = iota
+	Numeric
+	AlphaNumeric
+)
+
+func (e Encoding) getEncoder() encodeFn {
+	switch e {
+	case Auto:
+		return encodeAuto
+	case Numeric:
+		return encodeNumeric
+	case AlphaNumeric:
+		return encodeAlphaNumeric
+	}
+	return nil
+}
+
+func (e Encoding) String() string {
+	switch e {
+	case Auto:
+		return "Auto"
+	case Numeric:
+		return "Numeric"
+	case AlphaNumeric:
+		return "AlphaNumeric"
+	}
+	return ""
 }
 
 func Encode(content string, eccLevel ErrorCorrectionLevel, mode Encoding) (barcode.Barcode, error) {
-	bits, vi, err := mode.encode(content, eccLevel)
+	bits, vi, err := mode.getEncoder()(content, eccLevel)
 	if err != nil {
 		return nil, err
 	}
diff --git a/qr/encoder_test.go b/qr/encoder_test.go
deleted file mode 100644
index 068c264..0000000
--- a/qr/encoder_test.go
+++ /dev/null
@@ -1,11 +0,0 @@
-package qr
-
-import "testing"
-import "image/png"
-import "github.com/boombuler/barcode"
-import "os"
-
-func Test_EncodeQR(t *testing.T) {
-
-
-}
diff --git a/qr/numeric.go b/qr/numeric.go
index 2c2b078..0436904 100644
--- a/qr/numeric.go
+++ b/qr/numeric.go
@@ -7,16 +7,7 @@ import (
 	"strconv"
 )
 
-type numericEncoding struct {
-}
-
-var Numeric Encoding = numericEncoding{}
-
-func (ne numericEncoding) String() string {
-	return "Numeric"
-}
-
-func (ne numericEncoding) encode(content string, ecl ErrorCorrectionLevel) (*barcode.BitList, *versionInfo, error) {
+func encodeNumeric(content string, ecl ErrorCorrectionLevel) (*barcode.BitList, *versionInfo, error) {
 	contentBitCount := (len(content) / 3) * 10
 	switch len(content) % 3 {
 	case 1:
@@ -44,7 +35,7 @@ func (ne numericEncoding) encode(content string, ecl ErrorCorrectionLevel) (*bar
 
 		i, err := strconv.Atoi(curStr)
 		if err != nil || i < 0 {
-			return nil, nil, fmt.Errorf("\"%s\" can not be encoded as %s", content, ne)
+			return nil, nil, fmt.Errorf("\"%s\" can not be encoded as %s", content, Numeric)
 		}
 		var bitCnt byte
 		switch len(curStr) % 3 {
diff --git a/qr/numeric_test.go b/qr/numeric_test.go
index 2d8c0b4..22c6838 100644
--- a/qr/numeric_test.go
+++ b/qr/numeric_test.go
@@ -6,15 +6,16 @@ import (
 )
 
 func Test_NumericEncoding(t *testing.T) {
-	x, vi, err := Numeric.encode("01234567", H)
+	encode := Numeric.getEncoder()
+	x, vi, err := encode("01234567", H)
 	if x == nil || vi == nil || vi.Version != 1 || bytes.Compare(x.GetBytes(), []byte{16, 32, 12, 86, 97, 128, 236, 17, 236}) != 0 {
 		t.Error("\"01234567\" failed to encode")
 	}
-	x, vi, err = Numeric.encode("0123456789012345", H)
+	x, vi, err = encode("0123456789012345", H)
 	if x == nil || vi == nil || vi.Version != 1 || bytes.Compare(x.GetBytes(), []byte{16, 64, 12, 86, 106, 110, 20, 234, 80}) != 0 {
 		t.Error("\"0123456789012345\" failed to encode")
 	}
-	x, vi, err = Numeric.encode("foo", H)
+	x, vi, err = encode("foo", H)
 	if err == nil {
 		t.Error("Numeric encoding should not be able to encode \"foo\"")
 	}