QRコードを生成するには

# pip install "qrcode[pil]"
import qrcode
 
qr = qrcode.QRCode(error_correction=qrcode.constants.ERROR_CORRECT_M, box_size=10, border=4)
qr.add_data("https://example.com/hello")
qr.make(fit=True)
qr.make_image().save("qr.png")
print(qr.version)  # 2

// npm install qrcode
import QRCode from "qrcode";
 
const url = "https://example.com/hello";
await QRCode.toFile("qr.png", url, { errorCorrectionLevel: "M", margin: 4, scale: 10 });
console.log(QRCode.create(url, { errorCorrectionLevel: "M" }).version); // 2

// npm install qrcode && npm install -D @types/qrcode
import QRCode from "qrcode";
 
const url: string = "https://example.com/hello";
const options: QRCode.QRCodeToFileOptions = { errorCorrectionLevel: "M", margin: 4, scale: 10 };
await QRCode.toFile("qr.png", url, options);
console.log(QRCode.create(url, { errorCorrectionLevel: "M" }).version); // 2

// go get github.com/skip2/go-qrcode
package main
 
import (
	"fmt"
 
	"github.com/skip2/go-qrcode"
)
 
func main() {
	q, err := qrcode.New("https://example.com/hello", qrcode.Medium)
	if err != nil {
		panic(err)
	}
	if err := q.WriteFile(256, "qr.png"); err != nil {
		panic(err)
	}
	fmt.Println(q.VersionNumber) // 2
}

// Cargo.toml: qrcode = "0.14", image = "0.25"
use image::Luma;
use qrcode::{EcLevel, QrCode};
 
fn main() {
    let code = QrCode::with_error_correction_level("https://example.com/hello", EcLevel::M).unwrap();
    let img = code.render::<Luma<u8>>().min_dimensions(256, 256).build();
    img.save("qr.png").unwrap();
    println!("{:?}", code.version()); // Normal(2)
}

// ZXing の core と javase（3.5.4）をクラスパスに置く
import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
import java.nio.file.Path;
import java.util.Map;
 
public class Main {
    public static void main(String[] args) throws Exception {
        // 何も指定しないと誤り訂正レベルは L になる。他の言語に合わせて M を指定する
        Map<EncodeHintType, Object> hints = Map.of(
            EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M,
            EncodeHintType.MARGIN, 4);
        BitMatrix matrix = new QRCodeWriter()
            .encode("https://example.com/hello", BarcodeFormat.QR_CODE, 256, 256, hints);
        MatrixToImageWriter.writeToPath(matrix, "PNG", Path.of("qr.png"));
    }
}

// dotnet add package QRCoder
using System.IO;
using QRCoder;
 
using var generator = new QRCodeGenerator();
using var data = generator.CreateQrCode("https://example.com/hello", QRCodeGenerator.ECCLevel.M);
byte[] png = new PngByteQRCode(data).GetGraphic(10); // 1 モジュールを 10 ピクセルで描く
File.WriteAllBytes("qr.png", png);