add PDF export

qrcodegeneratorpdf.go

@@ -0,0 +1,194 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package qrbill
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"io"
+	"strings"
+	"time"
+
+	"github.com/makiuchi-d/gozxing"
+	"github.com/makiuchi-d/gozxing/qrcode/encoder"
+	"github.com/stapelberg/qrbill/internal/pdf"
+)
+
+// Image represents a PDF image object containing a DIN A4-sized page
+// scanned with 600dpi (i.e. into 4960x7016 pixels).
+type Image struct {
+	pdf.Common
+
+	Bounds image.Rectangle
+}
+
+// Objects implements Object.
+func (i *Image) Objects() []pdf.Object { return []pdf.Object{i} }
+
+// Encode implements Object.
+func (i *Image) Encode(w io.Writer, ids map[string]pdf.ObjectID) error {
+	_, err := fmt.Fprintf(w, `
+%d 0 obj
+<<
+  /Subtype /Form
+  /FormType 1
+  /Type /XObject
+  /ColorSpace /DeviceGray
+  /BBox [0 0 %d %d]
+  /Matrix [1 0 0 1 0 0]
+  /Resources << /ProcSet [/PDF] >>
+  /Length %d
+>>
+stream
+%s
+endstream
+endobj`,
+		int(i.Common.ID),
+		i.Bounds.Max.X,
+		i.Bounds.Max.Y,
+		len(i.Common.Stream),
+		i.Common.Stream)
+	return err
+}
+
+// renderResultPDF is a copy of renderResult from
+// gozxing/qrcode/qrcode_writer.go, adapted to output to PDF.
+func renderResultPDF(code *encoder.QRCode, width, height, quietZone int) ([]byte, error) {
+	input := code.GetMatrix()
+	if input == nil {
+		return nil, gozxing.NewWriterException("IllegalStateException")
+	}
+	inputWidth := input.GetWidth()
+	inputHeight := input.GetHeight()
+	qrWidth := inputWidth + (quietZone * 2)
+	qrHeight := inputHeight + (quietZone * 2)
+	outputWidth := qrWidth
+	if outputWidth < width {
+		outputWidth = width
+	}
+	outputHeight := qrHeight
+	if outputHeight < height {
+		outputHeight = height
+	}
+
+	multiple := outputWidth / qrWidth
+	if h := outputHeight / qrHeight; multiple > h {
+		multiple = h
+	}
+	// Padding includes both the quiet zone and the extra white pixels to accommodate the requested
+	// dimensions. For example, if input is 25x25 the QR will be 33x33 including the quiet zone.
+	// If the requested size is 200x160, the multiple will be 4, for a QR of 132x132. These will
+	// handle all the padding from 100x100 (the actual QR) up to 200x160.
+	leftPadding := (outputWidth - (inputWidth * multiple)) / 2
+	topPadding := (outputHeight - (inputHeight * multiple)) / 2
+
+	_, _ = leftPadding, topPadding
+
+	var codePath strings.Builder
+	codePath.WriteString("q\n")
+
+	// Change the application coordinate system to work like the SVG one does,
+	// for consistency between the different code paths. See also General
+	// Coordinate System Transformation, Page 18, Encapsulated PostScript File
+	// Format Specification:
+	// https://www.adobe.com/content/dam/acom/en/devnet/actionscript/articles/5002.EPSF_Spec.pdf
+	codePath.WriteString("1 0 0 -1 0 1265 cm\n")
+
+	for inputY, outputY := 0, topPadding; inputY < inputHeight; inputY, outputY = inputY+1, outputY+multiple {
+		// Write the contents of this row of the barcode
+		for inputX, outputX := 0, leftPadding; inputX < inputWidth; inputX, outputX = inputX+1, outputX+multiple {
+			if input.Get(inputX, inputY) == 1 {
+				codePath.WriteString(fmt.Sprintf("%d %d %d %d re\n",
+					outputX, outputY, multiple, multiple))
+				//eps.WriteString(fmt.Sprintf("%d %d %d %d F\n", outputX, outputY, multiple, multiple))
+			}
+		}
+	}
+	// Fill the whole path at once.
+	// This step is crucial:
+	// filling individual rectangles results in rendering artifacts
+	// in some PDF viewers at some zoom levels.
+	// Filling the whole path seems to prevent that entirely.
+	codePath.WriteString("0 g\n")
+	codePath.WriteString("f\n")
+
+	// overlay a PDF version of the swiss cross
+	codePath.WriteString("1 0 0 1 549 549 cm\n")
+
+	codePath.WriteString("1 g\n") // white
+	codePath.WriteString("0 0 166 166 re\n")
+	codePath.WriteString("f\n")
+
+	codePath.WriteString("0 g\n") // black
+	codePath.WriteString("12 12 142 142 re\n")
+	codePath.WriteString("f\n")
+
+	codePath.WriteString("1 g\n") // white
+	codePath.WriteString("36 66 94 28 re\n")
+	codePath.WriteString("f\n")
+	codePath.WriteString("68 34 30 92 re\n")
+	codePath.WriteString("f\n")
+
+	codePath.WriteString("Q\n")
+
+	kids := []pdf.Object{
+		&pdf.Page{
+			Common: pdf.Common{ObjectName: "page0"},
+			Resources: []pdf.Object{
+				&Image{
+					Common: pdf.Common{
+						ObjectName: "qr",
+						Stream:     []byte(codePath.String()),
+					},
+					Bounds: image.Rect(0, 0, 1265, 1265),
+				},
+			},
+			Parent: "pages",
+			Contents: []pdf.Object{
+				&pdf.Common{
+					ObjectName: "content0",
+					//[]byte("q 595.28 0 0 841.89 0.00 0.00 cm /code0 Do Q\n"),
+					Stream: []byte(`q
+0.12 0 0 0.12 0 0 cm
+/qr Do
+Q
+`),
+				},
+			},
+		},
+	}
+
+	doc := &pdf.Catalog{
+		Common: pdf.Common{ObjectName: "catalog"},
+		Pages: &pdf.Pages{
+			Common: pdf.Common{ObjectName: "pages"},
+			Kids:   kids,
+		},
+	}
+	info := &pdf.DocumentInfo{
+		Common:       pdf.Common{ObjectName: "info"},
+		CreationDate: time.Now(),
+		Producer:     "https://github.com/stapelberg/qrbill",
+		Title:        "QR-Bill",
+		// TODO: summarize the qr code in the subject
+	}
+	var buf bytes.Buffer
+	pdfEnc := pdf.NewEncoder(&buf)
+	if err := pdfEnc.Encode(doc, info); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}