HttpImg: make Http specific PDF interface.

Instead of forcing the type to be of gofpdf.Fpdf, we now use an
interface which could be whatever structure we want. This is useful for
third party libraries where they can define their own interface for the
PDF generator but still use these contribution packages.

HttpImg: add interface comment.

Barcode: implement specific PDF interface.

2 files changed, 38 insertions, 15 deletions

diff --git a/contrib/barcode/barcode.go b/contrib/barcode/barcode.go
index e49ac53..4a143da 100644
--- a/contrib/barcode/barcode.go
+++ b/contrib/barcode/barcode.go
@@ -20,6 +20,10 @@ package barcode
 import (
 	"bytes"
 	"errors"
+	"image/jpeg"
+	"io"
+	"strconv"
+
 	"github.com/boombuler/barcode"
 	"github.com/boombuler/barcode/codabar"
 	"github.com/boombuler/barcode/code128"
@@ -29,20 +33,28 @@ import (
 	"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
 
+// barcodePdf is a partial PDF implementation that only implements a subset of
+// functions that are required to add the barcode to the PDF.
+type barcodePdf interface {
+	GetConversionRatio() float64
+	GetImageInfo(imageStr string) *gofpdf.ImageInfoType
+	Image(imageNameStr string, x, y, w, h float64, flow bool, tp string, link int, linkStr string)
+	RegisterImageReader(imgName, tp string, r io.Reader) *gofpdf.ImageInfoType
+	SetError(err error)
+}
+
 // 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) {
+func Barcode(pdf barcodePdf, code string, x, y, w, h float64, flow bool) {
 	unscaled, ok := barcodes[code]
 
 	if !ok {
@@ -90,14 +102,14 @@ func Register(bcode barcode.Barcode) string {
 
 // 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 {
+func RegisterCodabar(pdf barcodePdf, 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 {
+func RegisterCode128(pdf barcodePdf, code string) string {
 	bcode, err := code128.Encode(code)
 	return registerBarcode(pdf, bcode, err)
 }
@@ -106,7 +118,7 @@ func RegisterCode128(pdf *gofpdf.Fpdf, code string) string {
 // 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 {
+func RegisterCode39(pdf barcodePdf, code string, includeChecksum, fullASCIIMode bool) string {
 	bcode, err := code39.Encode(code, includeChecksum, fullASCIIMode)
 	return registerBarcode(pdf, bcode, err)
 }
@@ -114,7 +126,7 @@ func RegisterCode39(pdf *gofpdf.Fpdf, code string, includeChecksum, fullASCIIMod
 // 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 {
+func RegisterDataMatrix(pdf barcodePdf, code string) string {
 	bcode, err := datamatrix.Encode(code)
 	return registerBarcode(pdf, bcode, err)
 }
@@ -122,7 +134,7 @@ func RegisterDataMatrix(pdf *gofpdf.Fpdf, code string) string {
 // 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 {
+func RegisterEAN(pdf barcodePdf, code string) string {
 	bcode, err := ean.Encode(code)
 	return registerBarcode(pdf, bcode, err)
 }
@@ -131,7 +143,7 @@ func RegisterEAN(pdf *gofpdf.Fpdf, code string) string {
 // 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 {
+func RegisterQR(pdf barcodePdf, code string, ecl qr.ErrorCorrectionLevel, mode qr.Encoding) string {
 	bcode, err := qr.Encode(code, ecl, mode)
 	return registerBarcode(pdf, bcode, err)
 }
@@ -141,7 +153,7 @@ func RegisterQR(pdf *gofpdf.Fpdf, code string, ecl qr.ErrorCorrectionLevel, mode
 // page.
 //
 // The interleaved bool is inherited from twooffive.Encode().
-func RegisterTwoOfFive(pdf *gofpdf.Fpdf, code string, interleaved bool) string {
+func RegisterTwoOfFive(pdf barcodePdf, code string, interleaved bool) string {
 	bcode, err := twooffive.Encode(code, interleaved)
 	return registerBarcode(pdf, bcode, err)
 }
@@ -150,7 +162,7 @@ func RegisterTwoOfFive(pdf *gofpdf.Fpdf, code string, interleaved bool) string {
 // 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 {
+func registerBarcode(pdf barcodePdf, bcode barcode.Barcode, err error) string {
 	if err != nil {
 		pdf.SetError(err)
 	}
@@ -178,7 +190,7 @@ func barcodeKey(bcode barcode.Barcode) string {
 // 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 {
+func registerScaledBarcode(pdf barcodePdf, code string, bcode barcode.Barcode) error {
 	buf := new(bytes.Buffer)
 	err := jpeg.Encode(buf, bcode, nil)
 
@@ -199,6 +211,6 @@ func registerScaledBarcode(pdf *gofpdf.Fpdf, code string, bcode barcode.Barcode)
 // 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 {
+func convertTo96Dpi(pdf barcodePdf, value float64) float64 {
 	return value * pdf.GetConversionRatio() / 72 * 96
 }
diff --git a/contrib/httpimg/httpimg.go b/contrib/httpimg/httpimg.go
index 10afcc8..7cbf281 100644
--- a/contrib/httpimg/httpimg.go
+++ b/contrib/httpimg/httpimg.go
@@ -1,14 +1,25 @@
 package httpimg
 
 import (
-	"github.com/jung-kurt/gofpdf"
+	"io"
 	"net/http"
+
+	"github.com/jung-kurt/gofpdf"
 )
 
+// httpimgPdf is a partial interface that only implements the functions we need
+// from the PDF generator to put the HTTP images on the PDF.
+type httpimgPdf interface {
+	GetImageInfo(imageStr string) *gofpdf.ImageInfoType
+	ImageTypeFromMime(mimeStr string) string
+	RegisterImageReader(imgName, tp string, r io.Reader) *gofpdf.ImageInfoType
+	SetError(err error)
+}
+
 // Register registers a HTTP image. Downloading the image from the provided URL
 // and adding it to the PDF but not adding it to the page. Use Image() with the
 // same URL to add the image to the page.
-func Register(f *gofpdf.Fpdf, urlStr, tp string) (info *gofpdf.ImageInfoType) {
+func Register(f httpimgPdf, urlStr, tp string) (info *gofpdf.ImageInfoType) {
 	info = f.GetImageInfo(urlStr)
 
 	if info != nil {