html部分:
js部分:
/**生成一个随机数**/
function randomNum(min, max) {
return Math.floor(Math.random() * (max - min) + min);
}
/**生成一个随机色**/
function randomColor(min, max) {
var r = randomNum(min, max);
var g = randomNum(min, max);
var b = randomNum(min, max);
return "rgb(" + r + "," + g + "," + b + ")";
}
var code = drawPic();
document.getElementById("changeImg").onclick =
function (e) {
e.preventDefault();
code = drawPic();
}
/**绘制验证码图片**/
function drawPic() {
var canvas = document.getElementById("canvas");
var width = canvas.width;
var height = canvas.height;
//获取该canvas的2D绘图环境
var ctx = canvas.getContext('2d');
ctx.textBaseline = 'bottom';
/**绘制背景色**/
ctx.fillStyle = randomColor(180, 240);
//颜色若太深可能导致看不清
ctx.fillRect(0, 0, width, height);
/**绘制文字**/
var str = 'ABCEFGHJKLMNPQRSTWXY123456789';
var code = "";
//生成四个验证码
for (var i = 1; i <= 4; i++) {
var txt = str[randomNum(0, str.length)];
code = code + txt;
ctx.fillStyle = randomColor(50, 160);
//随机生成字体颜色
ctx.font = randomNum(15, 40) + 'px SimHei';
//随机生成字体大小
var x = 10 + i * 25;
var y = randomNum(25, 35);
var deg = randomNum(-45, 45);
//修改坐标原点和旋转角度
ctx.translate(x, y);
ctx.rotate(deg * Math.PI / 180);
ctx.fillText(txt, 0, 0);
//恢复坐标原点和旋转角度
ctx.rotate(-deg * Math.PI / 180);
ctx.translate(-x, -y);
}
/**绘制干扰线**/
for (var i = 0; i < 3; i++) {
ctx.strokeStyle = randomColor(40, 180);
ctx.beginPath();
ctx.moveTo(randomNum(0, width / 2), randomNum(0, height / 2));
ctx.lineTo(randomNum(0, width / 2), randomNum(0, height));
ctx.stroke();
}
/**绘制干扰点**/
for (var i = 0; i < 50; i++) {
ctx.fillStyle = randomColor(255);
ctx.beginPath();
ctx.arc(randomNum(0, width), randomNum(0, height), 1, 0, 2 * Math.PI);
ctx.fill();
}
return code;
}