Add Barcode contribution package.

This package adds the ability to easily add a barcode to the PDF. This
barcode is generated with the github.com/boombuler/barcode package.

It adds wrappers for all the available barcode types through the
`Register()` and `Register<Type>()` methods. These register methods put
the barcode on the PDF, but not on the page. They will return a unique
key that should be used later on with the `Barcode()` method scale the
barcode and put it on the page.

3 files changed, 336 insertions, 0 deletions

diff --git a/contrib/barcode/barcode.go b/contrib/barcode/barcode.go
new file mode 100644
index 0000000..e49ac53
--- /dev/null
+++ b/contrib/barcode/barcode.go
@@ -0,0 +1,204 @@
+// Copyright (c) 2015 Jelmer Snoeck (Gmail: jelmer.snoeck)
+//
+// Permission to use, copy, modify, and distribute this software for any purpose
+// with or without fee is hereby granted, provided that the above copyright notice
+// and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+// FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+// Package barcode provides helper methods for adding barcodes of different
+// types to your pdf document. It relies on the github.com/boombuler/barcode
+// package for the barcode creation.
+package barcode
+
+import (
+	"bytes"
+	"errors"
+	"github.com/boombuler/barcode"
+	"github.com/boombuler/barcode/codabar"
+	"github.com/boombuler/barcode/code128"
+	"github.com/boombuler/barcode/code39"
+	"github.com/boombuler/barcode/datamatrix"
+	"github.com/boombuler/barcode/ean"
+	"github.com/boombuler/barcode/qr"
+	"github.com/boombuler/barcode/twooffive"
+	"github.com/jung-kurt/gofpdf"
+	"image/jpeg"
+	"strconv"
+)
+
+// barcodes represents the barcodes that have been registered through this
+// package. They will later be used to be scaled and put on the page.
+var barcodes map[string]barcode.Barcode
+
+// Barcode puts a registered barcode in the current page.
+//
+// The size should be specified in the units used to create the PDF document.
+//
+// Positioning with x, y and flow is inherited from Fpdf.Image().
+func Barcode(pdf *gofpdf.Fpdf, code string, x, y, w, h float64, flow bool) {
+	unscaled, ok := barcodes[code]
+
+	if !ok {
+		err := errors.New("Barcode not found")
+		pdf.SetError(err)
+		return
+	}
+
+	bname := uniqueBarcodeName(code, x, y)
+	info := pdf.GetImageInfo(bname)
+
+	if info == nil {
+		bcode, err := barcode.Scale(
+			unscaled,
+			int(convertTo96Dpi(pdf, w)),
+			int(convertTo96Dpi(pdf, h)),
+		)
+
+		if err != nil {
+			pdf.SetError(err)
+			return
+		}
+
+		err = registerScaledBarcode(pdf, bname, bcode)
+		if err != nil {
+			pdf.SetError(err)
+			return
+		}
+	}
+
+	pdf.Image(bname, x, y, 0, 0, flow, "jpg", 0, "")
+}
+
+// Register registers a barcode but does not put it on the page. Use Barcode()
+// with the same code to put the barcode on the PDF page.
+func Register(bcode barcode.Barcode) string {
+	if len(barcodes) == 0 {
+		barcodes = make(map[string]barcode.Barcode)
+	}
+
+	key := barcodeKey(bcode)
+	barcodes[key] = bcode
+	return key
+}
+
+// RegisterCodabar registers a barcode of type Codabar to the PDF, but not to
+// the page. Use Barcode() with the return value to put the barcode on the page.
+func RegisterCodabar(pdf *gofpdf.Fpdf, code string) string {
+	bcode, err := codabar.Encode(code)
+	return registerBarcode(pdf, bcode, err)
+}
+
+// RegisterCode128 registers a barcode of type Code128 to the PDF, but not to
+// the page. Use Barcode() with the return value to put the barcode on the page.
+func RegisterCode128(pdf *gofpdf.Fpdf, code string) string {
+	bcode, err := code128.Encode(code)
+	return registerBarcode(pdf, bcode, err)
+}
+
+// RegisterCode39 registers a barcode of type Code39 to the PDF, but not to
+// the page. Use Barcode() with the return value to put the barcode on the page.
+//
+// includeChecksum and fullASCIIMode are inherited from code39.Encode().
+func RegisterCode39(pdf *gofpdf.Fpdf, code string, includeChecksum, fullASCIIMode bool) string {
+	bcode, err := code39.Encode(code, includeChecksum, fullASCIIMode)
+	return registerBarcode(pdf, bcode, err)
+}
+
+// RegisterDataMatrix registers a barcode of type DataMatrix to the PDF, but not
+// to the page. Use Barcode() with the return value to put the barcode on the
+// page.
+func RegisterDataMatrix(pdf *gofpdf.Fpdf, code string) string {
+	bcode, err := datamatrix.Encode(code)
+	return registerBarcode(pdf, bcode, err)
+}
+
+// RegisterEAN registers a barcode of type EAN to the PDF, but not to the page.
+// It will automatically detect if the barcode is EAN8 or EAN13. Use Barcode()
+// with the return value to put the barcode on the page.
+func RegisterEAN(pdf *gofpdf.Fpdf, code string) string {
+	bcode, err := ean.Encode(code)
+	return registerBarcode(pdf, bcode, err)
+}
+
+// RegisterQR registers a barcode of type QR to the PDF, but not to the page.
+// Use Barcode() with the return value to put the barcode on the page.
+//
+// The ErrorCorrectionLevel and Encoding mode are inherited from qr.Encode().
+func RegisterQR(pdf *gofpdf.Fpdf, code string, ecl qr.ErrorCorrectionLevel, mode qr.Encoding) string {
+	bcode, err := qr.Encode(code, ecl, mode)
+	return registerBarcode(pdf, bcode, err)
+}
+
+// RegisterTwoOfFive registers a barcode of type TwoOfFive to the PDF, but not
+// to the page. Use Barcode() with the return value to put the barcode on the
+// page.
+//
+// The interleaved bool is inherited from twooffive.Encode().
+func RegisterTwoOfFive(pdf *gofpdf.Fpdf, code string, interleaved bool) string {
+	bcode, err := twooffive.Encode(code, interleaved)
+	return registerBarcode(pdf, bcode, err)
+}
+
+// registerBarcode registers a barcode internally using the Register() function.
+// In case of an error generating the barcode it will not be registered and will
+// set an error on the PDF. It will return a unique key for the barcode type and
+// content that can be used to put the barcode on the page.
+func registerBarcode(pdf *gofpdf.Fpdf, bcode barcode.Barcode, err error) string {
+	if err != nil {
+		pdf.SetError(err)
+	}
+
+	return Register(bcode)
+}
+
+// uniqueBarcodeName makes sure every barcode has a unique name for its
+// dimensions. Scaling a barcode image results in quality loss, which could be
+// a problem for barcode readers.
+func uniqueBarcodeName(code string, x, y float64) string {
+	xStr := strconv.FormatFloat(x, 'E', -1, 64)
+	yStr := strconv.FormatFloat(y, 'E', -1, 64)
+
+	return "barcode-" + code + "-" + xStr + yStr
+}
+
+// barcodeKey combines the code type and code value into a unique identifier for
+// a barcode type. This is so that we can store several barcodes with the same
+// code but different type in the barcodes map.
+func barcodeKey(bcode barcode.Barcode) string {
+	return bcode.Metadata().CodeKind + bcode.Content()
+}
+
+// registerScaledBarcode registers a barcode with its exact dimensions to the
+// PDF but does not put it on the page. Use Fpdf.Image() with the same code to
+// add the barcode to the page.
+func registerScaledBarcode(pdf *gofpdf.Fpdf, code string, bcode barcode.Barcode) error {
+	buf := new(bytes.Buffer)
+	err := jpeg.Encode(buf, bcode, nil)
+
+	if err != nil {
+		return err
+	}
+
+	reader := bytes.NewReader(buf.Bytes())
+	pdf.RegisterImageReader(code, "jpg", reader)
+
+	return nil
+}
+
+// convertTo96DPI converts the given value, which is based on a 72 DPI value
+// like the rest of the PDF document, to a 96 DPI value that is required for
+// an Image.
+//
+// Doing this through the Fpdf.Image() function would mean that it uses a 72 DPI
+// value and stretches it to a 96 DPI value. This results in quality loss which
+// could be problematic for barcode scanners.
+func convertTo96Dpi(pdf *gofpdf.Fpdf, value float64) float64 {
+	return value * pdf.GetConversionRatio() / 72 * 96
+}
diff --git a/contrib/barcode/barcode_test.go b/contrib/barcode/barcode_test.go
new file mode 100644
index 0000000..c12ff12
--- /dev/null
+++ b/contrib/barcode/barcode_test.go
@@ -0,0 +1,126 @@
+package barcode_test
+
+import (
+	"github.com/boombuler/barcode/code128"
+	"github.com/boombuler/barcode/qr"
+	"github.com/jung-kurt/gofpdf"
+	"github.com/jung-kurt/gofpdf/contrib/barcode"
+	"github.com/jung-kurt/gofpdf/internal/example"
+)
+
+func createPdf() (pdf *gofpdf.Fpdf) {
+	pdf = gofpdf.New("L", "mm", "A4", "")
+	pdf.SetFont("Helvetica", "", 12)
+	pdf.SetFillColor(200, 200, 220)
+	pdf.AddPage()
+	return
+}
+
+func ExampleRegister() {
+	pdf := createPdf()
+
+	fileStr := example.Filename("contrib_barcode_Register")
+
+	bcode, err := code128.Encode("gofpdf")
+
+	if err == nil {
+		key := barcode.Register(bcode)
+		barcode.Barcode(pdf, key, 15, 15, 100, 10, false)
+	}
+
+	err = pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated ../../pdf/contrib_barcode_Register.pdf
+}
+
+func ExampleRegisterCodabar() {
+	pdf := createPdf()
+
+	key := barcode.RegisterCode128(pdf, "codabar")
+	barcode.Barcode(pdf, key, 15, 15, 100, 10, false)
+
+	fileStr := example.Filename("contrib_barcode_RegisterCodabar")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated ../../pdf/contrib_barcode_RegisterCodabar.pdf
+}
+
+func ExampleRegisterCode128() {
+	pdf := createPdf()
+
+	key := barcode.RegisterCode128(pdf, "code128")
+	barcode.Barcode(pdf, key, 15, 15, 100, 10, false)
+
+	fileStr := example.Filename("contrib_barcode_RegisterCode128")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated ../../pdf/contrib_barcode_RegisterCode128.pdf
+}
+
+func ExampleRegisterCode39() {
+	pdf := createPdf()
+
+	key := barcode.RegisterCode39(pdf, "CODE39", false, true)
+	barcode.Barcode(pdf, key, 15, 15, 100, 10, false)
+
+	fileStr := example.Filename("contrib_barcode_RegisterCode39")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated ../../pdf/contrib_barcode_RegisterCode39.pdf
+}
+
+func ExampleRegisterDataMatrix() {
+	pdf := createPdf()
+
+	key := barcode.RegisterDataMatrix(pdf, "datamatrix")
+	barcode.Barcode(pdf, key, 15, 15, 20, 20, false)
+
+	fileStr := example.Filename("contrib_barcode_RegisterDataMatrix")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated ../../pdf/contrib_barcode_RegisterDataMatrix.pdf
+}
+
+func ExampleRegisterEAN() {
+	pdf := createPdf()
+
+	key := barcode.RegisterEAN(pdf, "96385074")
+	barcode.Barcode(pdf, key, 15, 15, 100, 10, false)
+
+	fileStr := example.Filename("contrib_barcode_RegisterEAN")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated ../../pdf/contrib_barcode_RegisterEAN.pdf
+}
+
+func ExampleRegisterQR() {
+	pdf := createPdf()
+
+	key := barcode.RegisterQR(pdf, "qrcode", qr.H, qr.Unicode)
+	barcode.Barcode(pdf, key, 15, 15, 20, 20, false)
+
+	fileStr := example.Filename("contrib_barcode_RegisterQR")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated ../../pdf/contrib_barcode_RegisterQR.pdf
+}
+
+func ExampleRegisterTwoOfFive() {
+	pdf := createPdf()
+
+	key := barcode.RegisterTwoOfFive(pdf, "1234567895", true)
+	barcode.Barcode(pdf, key, 15, 15, 100, 20, false)
+
+	fileStr := example.Filename("contrib_barcode_RegisterTwoOfFive")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated ../../pdf/contrib_barcode_RegisterTwoOfFive.pdf
+}
diff --git a/fpdf.go b/fpdf.go
index d77fd4b..da3d92a 100644
--- a/fpdf.go
+++ b/fpdf.go
@@ -2365,6 +2365,12 @@ func (f *Fpdf) GetImageInfo(imageStr string) (info *ImageInfoType) {
 	return f.images[imageStr]
 }
 
+// GetConversionRatio returns the conversion ratio based on the unit given when
+// creating the PDF.
+func (f *Fpdf) GetConversionRatio() float64 {
+	return f.k
+}
+
 // GetXY returns the abscissa and ordinate of the current position.
 //
 // Note: the value returned for the abscissa will be affected by the current