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datamatrix: GS1 DataMatrix support added #86

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datamatrix: GS1 DataMatrix support added #86

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30 changes: 30 additions & 0 deletions datamatrix/datamatrix_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -100,3 +100,33 @@ func Test_Issue12(t *testing.T) {
}
}
}

func Test_GS1DataMatrix(t *testing.T) {
// Example 2 from the GS1 DataMatrix Guideline.
//
// (01)09501101020917(17)190508(10)ABCD1234(21)10
//
// See: https://www.gs1.org/standards/gs1-datamatrix-guideline/25#2-Encoding-data+2-3-Human-readable-interpretation-(HRI)
data := new(bytes.Buffer)
data.WriteByte(FNC1) // Start Character
data.WriteString("0109501101020917") // AI (01)
data.WriteString("17190508") // AI (17)
data.WriteString("10ABCD1234") // AI (10) does not have pre-defined length
data.WriteByte(FNC1) // Separator Character
data.WriteString("2110") // AI (20)

// Codewords from decoding example 2 with "dmtxread -c".
wantedData := []byte{
232, // FNC1
131, 139, 180, 141, 131, 132, 139, 147,
147, 149, 135, 138,
140, 66, 67, 68, 69, 142, 164,
232, // FNC1
151, 140,
}

realData := encodeText(data.String())
if bytes.Compare(realData, wantedData) != 0 {
t.Errorf("GS1 DataMatrix encoding failed\nwant: %v\ngot: %v\n", wantedData, realData)
}
}
11 changes: 11 additions & 0 deletions datamatrix/encoder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,13 @@ import (
"github.com/boombuler/barcode"
)

// FNC1 is the codeword for the Function 1 Symbol Character to
// differentiate a GS1 DataMatrix from other Data Matrix symbols.
//
// It is used as both a start character and a separator of GS1 element
// strings.
const FNC1 byte = 232

// Encode returns a Datamatrix barcode for the given content and color scheme
func EncodeWithColor(content string, color barcode.ColorScheme) (barcode.Barcode, error) {
data := encodeText(content)
Expand Down Expand Up @@ -48,6 +55,8 @@ func encodeText(content string) []byte {
var result []byte
input := []byte(content)

isGS1 := len(input) > 0 && input[0] == FNC1

for i := 0; i < len(input); {
c := input[i]
i++
Expand All @@ -58,6 +67,8 @@ func encodeText(content string) []byte {
i++
cw := byte(((c-'0')*10 + (c2 - '0')) + 130)
result = append(result, cw)
} else if isGS1 && c == FNC1 {
result = append(result, c)
} else if c > 127 {
// not correct... needs to be redone later...
result = append(result, 235, c-127)
Expand Down