public class Imagetest extends HttpServlet {
//将要添加进图片的字符当然这些字符是被随机进去的
public static final char[] CHARS={'a','b','c','d','e','f','g','h','i','j','k','m','n','o','q','r','s','t','u','v','w','x','y','z','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','J','K','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
//创建随机对象Random对象
public static Random random=new Random();
//获取随机字符的方法返回字符串
public static String getRandomString(){
StringBuilder builder=new StringBuilder();
for (int i = 0; i < 6; i++) {//每次要六个字符
builder.append(CHARS[random.nextInt(CHARS.length)]);
}
return builder.toString();
}
//图片背景的颜色
public static Color getColor(){
return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
}
//获取当前图片的反色为了让图片颜色和图片的颜色形成鲜明的对比
public static Color getReverseColor(Color c){
return new Color(255-c.getRed(),255-c.getBlue(),255-c.getGreen());
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("00000000000000000000000000000000");
response.setContentType("imae/jpeg");
String randomString=getRandomString();//获取在之前随机出来的数字
//将之前的随机字符转放到session中一边在前端调用
request.getSession(true).setAttribute("randomString", randomString);
//从现在开始画图片
//第一步设置图片的高度和宽度
int width=100;
int height=30;
//获取图片的颜色
Color color=getColor();
//获取图片的反色
Color reveserColor=getReverseColor(color);
//创建一个以红蓝绿为基色的图片
BufferedImage bi=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D g=bi.createGraphics();//用之前的图片来创建一个画图对象
//设置在图片上的字体
g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,18));//Font构造中的参数:字体的样式,字体加粗,字体大小
//设置颜色
g.setColor(color);
//绘制背景
g.fillRect(0, 0, width, height);//以浏览器的左上角为原点,以width为宽度,以height为高度
//设置颜色(这里是给字体设置颜色,所以取的是反色)
g.setColor(reveserColor);
//在已经画好的图片上写入随机好的字符
g.drawString(randomString, 18, 20);
//下面的工作是为了效果更加明显为图片加入噪音点
for (int i = 0,n=random.nextInt(100); i <n; i++) {
g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);//在一定范围内画噪音点
}
//利用字节流将图片转成JPEG格式
ServletOutputStream out=response.getOutputStream();
JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);//编码器
encoder.encode(bi);//对刚刚画好的图片进行编码
out.flush();//输出到客户端
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);//这样写的目的大家一目了然
}
}
//web.xml的配置情况
<servlet>
<servlet-name>Imagetest</servlet-name>
<servlet-class>Imagetest</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Imagetest</servlet-name>
<url-pattern>/servlet/Imagetest</url-pattern>
</servlet-mapping>
//前台JSP代码部分
<img src="servlet/Imagetest"></img>
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