一、前言
在实际应用中，我们可能需要将用户姓名作为头像显示，那么我们可以通过Java来实现。

二、如何实现
1.定义一个工具类，代码如下：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.RoundRectangle2D;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Base64;
import java.util.Random;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class CreateNamePictureUtil {
    private static final Logger log = LoggerFactory.getLogger(CreateNamePictureUtil.class);

    public static final String BASE64_PREFIX = "data:image/png;base64,";

    public static String createBase64Avatar(String userName) throws IOException {
        return BASE64_PREFIX + new String(Base64.getEncoder().encode(generateImg(userName)));
    }
  /**
     * 绘制字体头像 默认大小100*100
     * 如果是英文名，只显示首字母大写
     * 如果是中文名，只显示最后两个字
     * @param name
     * @throws IOException
     */
    public static byte[] generateImg(String name)
            throws IOException {
        int width = 100;
        int height = 100;
        int nameLen = name.length();
        String nameWritten;
        // 如果用户输入的姓名少于等于2个字符，不用截取
        if (nameLen <= 2) {
            nameWritten = name;
        } else {
            // 如果用户输入的姓名大于等于3个字符，截取后面两位
            String first = name.substring(0, 1);
            if (isChinese(first)) {
                // 截取倒数两位汉字
                nameWritten = name.substring(nameLen - 2);
            } else {
                // 截取后面的两个英文字母
                nameWritten = name.substring(nameLen - 2).toUpperCase();
            }
        }

       BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        Graphics2D g2 = (Graphics2D) bi.getGraphics();
        g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
                RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        g2.setBackground(getRandomColor());

        g2.clearRect(0, 0, width, height);
        g2.setPaint(Color.WHITE);
        Font font = null;
        // 两个字及以上
        if(nameWritten.length() >= 2) {
            font = new Font("微软雅黑", Font.PLAIN, 55);
            g2.setFont(font);

            String firstWritten = nameWritten.substring(nameWritten.length() -1, nameWritten.length());
            FontMetrics fm = g2.getFontMetrics(font);
            int textWidth = fm.stringWidth(firstWritten);
            int widthX = (width - textWidth) / 2;
if (!isChinese(firstWritten)) {
                String firstWrittenUpper = firstWritten.toUpperCase();
                g2.drawString(firstWrittenUpper, widthX, 70);
            } else {
                g2.drawString(firstWritten, widthX, 70);
            }
        }
        // 一个字
        if(nameWritten.length() ==1) {
            // 中文
            if(isChinese(nameWritten)) {
                font = new Font("微软雅黑", Font.PLAIN, 55);
                g2.setFont(font);
                g2.drawString(nameWritten, 25, 70);
            }
            // 英文
            else {
                font = new Font("微软雅黑", Font.PLAIN, 55);
                g2.setFont(font);
                FontMetrics fm = g2.getFontMetrics(font);
                int textWidth = fm.stringWidth(nameWritten);
                int widthX = (width - textWidth) / 2;
                g2.drawString(nameWritten.toUpperCase(), widthX, 100);
            }
        }
        log.info("name is {}",nameWritten);
        BufferedImage rounded = makeRoundedCorner(bi, 99);
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        ImageIO.write(rounded, "png", byteArrayOutputStream);
        return byteArrayOutputStream.toByteArray();
    }
     /**
     * 判断字符串是否为中文
     * @param str
     * @return
     */
    public static boolean isChinese(String str) {
        String regEx = "[\\u4e00-\\u9fa5]+";
        Pattern p = Pattern.compile(regEx);
        Matcher m = p.matcher(str);
        if (m.find())
            return true;
        else
            return false;
    }

    /**
     * 获得随机颜色
     * @return
     */
    public static Color getRandomColor() {
        String[] beautifulColors =
                new String[]{"141,224,157", "116,219,216", "120,195,255", "167,157,255", "255,161,217",
                        "252,136,136", "247,199,94"};
        int len = beautifulColors.length;
        Random random = new Random();
        String[] color = beautifulColors[random.nextInt(len)].split(",");
        return new Color(Integer.parseInt(color[0]), Integer.parseInt(color[1]),
                Integer.parseInt(color[2]));
    }

    /**
     * 图片做圆角处理
     * @param image
     * @param cornerRadius
     * @return
     */
    public static BufferedImage makeRoundedCorner(BufferedImage image, int cornerRadius){
        int w = image.getWidth();
        int h = image.getHeight();
        BufferedImage output = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2 = output.createGraphics();
        g2.setComposite(AlphaComposite.Src);
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setColor(Color.WHITE);
        g2.fill(new RoundRectangle2D.Float(0, 0, w, h, cornerRadius, cornerRadius));
        g2.setComposite(AlphaComposite.SrcAtop);
        g2.drawImage(image, 0, 0, null);
        g2.dispose();
        return output;
    }

2.接着我们通过main方法测试下：

public class TestDemo{
	public static void main(String[] args) throws IOException {
        System.out.println(CreateNamePictureUtil.createBase64Avatar("王小五"));
    }
}

执行后，结果如下：

有兴趣可以试试！！