qr_labels/main.go

package main

import (
	"fmt"
	"log/slog"

	"codeberg.org/go-pdf/fpdf"
	"github.com/yeqown/go-qrcode/v2"
	"github.com/yeqown/go-qrcode/writer/standard"
)

var cols = 4
var rows = 4
var qrSize = 50.0
var fontSize = 32.0 // pts
var fontSizeMM = fontSize / 72 * 25.4
var text = "meow!"

var textTopPadding = 5.0
var qrTopPadding = 5.0

// var probably some padding instead of offsets for qr/font placement

func main() {

	qrc, err := qrcode.New("https://nanocat.net/dom/sdfih/dsifj/sidhof/sdifho/sdfiuoh/safiuho")

	if err != nil {
		fmt.Printf("could not generate QRCode: %v", err)
		return
	}

	b := newBWC()
	qrBytes := standard.NewWithWriter(&b,
		// standard.WithQRWidth(uint8(qrSize)),
		standard.WithBorderWidth(0),
		standard.WithBuiltinImageEncoder(standard.PNG_FORMAT),
		// standard.WithCircleShape(),
		// standard.WithFgGradient(&standard.LinearGradient{
		// 	Stops: []standard.ColorStop{{
		// 		T: 0.0,
		// 		Color: color.RGBA{
		// 			R: 255,
		// 			G: 0,
		// 			B: 0,
		// 			A: 0,
		// 		},
		// 	}, {
		// 		T: 1.0,
		// 		Color: color.RGBA{
		// 			R: 0,
		// 			G: 255,
		// 			B: 0,
		// 			A: 0,
		// 		},
		// 	}},
		// 	Angle: 45,
		// }),
	)

	// save file
	if err = qrc.Save(qrBytes); err != nil {
		fmt.Printf("could not save image: %v", err)
	}
	// dim := qrc.Dimension()

	pdf := fpdf.New("P", "mm", "A4", "")
	pdf.SetMargins(0, 0, 0)
	pageWidth, pageHeight := pdf.GetPageSize()

	// register the qr
	pdf.RegisterImageOptionsReader("qr", fpdf.ImageOptions{
		ImageType:             "png",
		ReadDpi:               false,
		AllowNegativePosition: false,
	}, b)

	// info := pdf.GetImageInfo("qr")
	// panic(info.Height())

	pdf.AddPage()
	pdf.SetFont("Arial", "B", float64(fontSize))

	textWidth := pdf.GetStringWidth(text)

	colWidth := pageWidth / float64(cols)
	rowHeight := pageHeight / float64(rows)

	if textTopPadding+fontSizeMM+qrTopPadding+qrSize > rowHeight {
		slog.Warn("qr is too big for row")
	}

	if qrSize > colWidth {
		slog.Warn("qr is too big for column")
	}

	if textWidth > colWidth {
		slog.Warn("text probably too wide")
	}

	for rowIdx := range rows {
		for colIdx := range cols {
			topLeftX := colWidth * float64(colIdx)
			topLeftY := rowHeight * float64(rowIdx)

			// label at the top
			pdf.Text(
				topLeftX+colWidth/2-textWidth/2,
				topLeftY+textTopPadding+fontSizeMM,
				text, // +fmt.Sprintf("%d/%d", rowIdx, colIdx)
			)

			// qr at the bottom
			pdf.ImageOptions("qr",
				topLeftX+colWidth/2-qrSize/2,
				topLeftY+textTopPadding+fontSizeMM+qrTopPadding,
				qrSize, qrSize,
				false,
				fpdf.ImageOptions{AllowNegativePosition: true}, 0, "")
		}
	}

	err = pdf.OutputFileAndClose("hello.pdf")
	if err != nil {
		panic(err)
	}
	fmt.Println(pageWidth, pageHeight)
}