Java根据Hash生成用户头像

Github 等很多应用。在用户注册后，都会为你随机生成一个头像。非常的简约。实用。

    import java.awt.Color;
    import java.awt.Graphics2D;
    import java.awt.image.BufferedImage;
    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.math.BigInteger;
    import java.util.Base64;
    import java.util.Random;
    
    import javax.imageio.ImageIO;
    
    public class AvatarHelper {
    	
    	// 可以直接在<img/>标签或者浏览器地址栏预览的base64编码头
    	public static final String BASE64_PREFIX = "data:image/png;base64,";
    
    	/**
    	 * 生成头像的base64编码
    	 * @param id
    	 * @return
    	 * @throws IOException
    	 */
    	public static String createBase64Avatar(int id) throws IOException {
    		return new String(Base64.getEncoder().encode(create(id)));
    	}
    
    	/**
    	 * 根据id生成一个头像，颜色随机。如果是使用hashCode()值的话，值可能为负数。需要要注意。
    	 * @param id
    	 * @return
    	 * @throws IOException
    	 */
    	public static byte[] create(int id) throws IOException {
    		int width = 20;
    		int grid = 5;
    		int padding = width / 2;
    		int size = width * grid + width;
    		BufferedImage img = new BufferedImage(size, size, BufferedImage.TYPE_INT_RGB);
    		Graphics2D _2d = img.createGraphics();
    		_2d.setColor(new Color(240, 240, 240));
    		_2d.fillRect(0, 0, size, size);
    		_2d.setColor(randomColor(80, 200));
    		char[] idchars = createIdent(id);
    		int i = idchars.length;
    		for (int x = 0; x < Math.ceil(grid / 2.0); x++) {
    			for (int y = 0; y < grid; y++) {
    				if (idchars[--i] < 53) {
    					_2d.fillRect((padding + x * width), (padding + y * width), width, width);
    					if (x < Math.floor(grid / 2)) {
    						_2d.fillRect((padding + ((grid - 1) - x) * width), (padding + y * width), width, width);
    					}
    				}
    			}
    		}
    		_2d.dispose();
    		ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    		ImageIO.write(img, "png", byteArrayOutputStream);
    		return byteArrayOutputStream.toByteArray();
    	}
    
    	private static Color randomColor(int fc, int bc) {
    		Random random = new Random();
    		if (fc > 255) {
    			fc = 255;
    		}
    		if (bc > 255) {
    			bc = 255;
    		}
    		int r = fc + random.nextInt(Math.abs(bc - fc));
    		int g = fc + random.nextInt(Math.abs(bc - fc));
    		int b = fc + random.nextInt(Math.abs(bc - fc));
    		return new Color(r, g, b);
    	}
    
    	private static char[] createIdent(int id) {
    		BigInteger bi_content = new BigInteger((id + "").getBytes());
    		BigInteger bi = new BigInteger(id + "identicon" + id, 36);
    		bi = bi.xor(bi_content);
    		return bi.toString(10).toCharArray();
    	}
    }

    public class Main {
    	public static void main(String[] args) throws Exception {
    		String avatar = AvatarHelper.createBase64Avatar(Math.abs("springboot.io".hashCode()));
    		System.out.println(AvatarHelper.BASE64_PREFIX + avatar);
    	}
    }