java 实现二维码生成工具类

    /**
    * The message to put into QrCode
    */
    private String msg;
    
    
    /**
    * qrcode center logo
    */
    private String logo;
    
    
    /**
    * qrcode image width
    */
    private Integer w;
    
    
    /**
    * qrcode image height
    */
    private Integer h;
    
    
    /**
    * qrcode bgcolor, default white
    */
    private Integer offColor;
    
    
    /**
    * qrcode msg color, default black
    */
    private Integer onColor;
    
    
    /**
    * qrcode message's code, default UTF-8
    */
    private String code;
    
    
    /**
    * 0 - 4
    */
    private Integer padding;
    
    
    /**
    * error level, default H
    */
    private ErrorCorrectionLevel errorCorrection;
    
    
    /**
    * output qrcode image type, default png
    */
    private String picType;
    ```

- 二维码生成

    生成二维码核心代码 
`QRCode code = Encoder.encode(qrCodeConfig.getMsg(), errorCorrectionLevel, qrCodeConfig.getHints());`

    生成的code中， 就包含了二维码矩阵， 剩下的就是将矩阵渲染输出的问题， 输出没什么好说的，这里指出一点原生的zxing生成二维码的白边可能特别大，本工具类内部做了兼容，[点我查看大白边修复指南](https://my.oschina.net/u/566591/blog/872770)


```java
    /**
     * 对 zxing 的 QRCodeWriter 进行扩展, 解决白边过多的问题
     * <p/>
     * 源码参考 {@link com.google.zxing.qrcode.QRCodeWriter#encode(String, BarcodeFormat, int, int, Map)}
     */
    private static BitMatrix encode(QrCodeConfig qrCodeConfig) throws WriterException {
        ErrorCorrectionLevel errorCorrectionLevel = ErrorCorrectionLevel.L;
        int quietZone = 1;
        if (qrCodeConfig.getHints() != null) {
            if (qrCodeConfig.getHints().containsKey(EncodeHintType.ERROR_CORRECTION)) {
                errorCorrectionLevel = ErrorCorrectionLevel.valueOf(qrCodeConfig.getHints().get(EncodeHintType.ERROR_CORRECTION).toString());
            }
            if (qrCodeConfig.getHints().containsKey(EncodeHintType.MARGIN)) {
                quietZone = Integer.parseInt(qrCodeConfig.getHints().get(EncodeHintType.MARGIN).toString());
            }

            if (quietZone > QUIET_ZONE_SIZE) {
                quietZone = QUIET_ZONE_SIZE;
            } else if (quietZone < 0) {
                quietZone = 0;
            }
        }

        QRCode code = Encoder.encode(qrCodeConfig.getMsg(), errorCorrectionLevel, qrCodeConfig.getHints());
        return renderResult(code, qrCodeConfig.getW(), qrCodeConfig.getH(), quietZone);
    }
    ```

## 3. 使用说明

写完了就要开始实际用，写了个测试类，贴出如下

```java
/**
     * 测试二维码
     */
    @Test
    public void testGenQrCode() {
        String msg = "create qrcode!!!";

        // 简单的生成
        QrCodeConfig qrCodeConfig = QrCodeGenWrapper.createQrCodeConfig()
                .setMsg(msg)
                .build();

        try {
            boolean ans = QrCodeGenWrapper.asFile(qrCodeConfig, "qrcode/gen.png");
            System.out.println(ans);
        } catch (Exception e) {
            System.out.println("create qrcode error! e: " + e);
            Assert.assertTrue(false);
        }


        //生成红色的二维码 300x300, 无边框
        try {
            boolean ans = QrCodeGenWrapper.createQrCodeConfig()
                    .setMsg(msg)
                    .setW(300)
                    .setOnColor(0xffff0000)
                    .setOffColor(0xffffffff)
                    .setPadding(0)
                    .asFile("qrcode/gen_300x300.png");
            System.out.println(ans);
        } catch (Exception e) {
            System.out.println("create qrcode error! e: " + e);
            Assert.assertTrue(false);
        }


        // 生成带logo的二维码
        try {
            String logo = "https://git.oschina.net/uploads/34/2334_liuyueyi.png";
            boolean ans = QrCodeGenWrapper.createQrCodeConfig()
                    .setMsg(msg)
                    .setW(300)
                    .setOnColor(0xffff0000)
                    .setOffColor(0xffffffff)
                    .setPadding(0)
                    .setLogo(logo)
                    .asFile("qrcode/gen_300x300_logo.png");
            System.out.println(ans);
        } catch (Exception e) {
            System.out.println("create qrcode error! e: " + e);
            Assert.assertTrue(false);
        }


        // 根据本地文件生成待logo的二维码
        try {
            String logo = "qrcode/logo.png";
            boolean ans = QrCodeGenWrapper.createQrCodeConfig()
                    .setMsg(msg)
                    .setW(300)
                    .setOnColor(0xffff0000)
                    .setOffColor(0xffffffff)
                    .setPadding(0)
                    .setLogo(logo)
                    .asFile("qrcode/gen_300x300_logo_v2.png");
            System.out.println(ans);
        } catch (Exception e) {
            System.out.println("create qrcode error! e: " + e);
            Assert.assertTrue(false);
        }
    }