canvas 实现随机验证码图片

<template>
<div class="canvas-box" :style="{ height: contentHeight + 'px' }">
    <canvas id="id-canvas" class="id-canvas" :width="contentWidth" :height="contentHeight"></canvas>
    </div>
</template>

<script setup lang="ts" name="Identify">
    import { onMounted, watch } from "vue";

    interface IProps {
        identifyCode?: string; // 默认注册码
        fontSizeMin?: number; // 字体最小值
        fontSizeMax?: number; // 字体最大值
        backgroundColorMin?: number; // 验证码图片背景色最小值
        backgroundColorMax?: number; // 验证码图片背景色最小值
        dotColorMin?: number; // 背景干扰点最小值
        dotColorMax?: number; // 背景干扰点最小值
        contentWidth?: number; // 容器宽度
        contentHeight?: number; // 容器高度
    }
        const props = withDefaults(defineProps<IProps>(), {
            identifyCode: "1234",
            fontSizeMin: 28,
            fontSizeMax: 38,
            backgroundColorMin: 200,
            backgroundColorMax: 220,
            dotColorMin: 30,
            dotColorMax: 120,
            contentWidth: 100,
            contentHeight: 40
        });
        // 生成一个随机数
        const randomNum = (min: number, max: number) => {
            return Math.floor(Math.random() * (max - min) + min);
        };

        // 生成一个随机的颜色
        const randomColor = (min: number, max: number) => {
            let r = randomNum(min, max);
            let g = randomNum(min, max);
            let b = randomNum(min, max);
            return "rgb(" + r + "," + g + "," + b + ")";
        };

        const drawPic = () => {
            let canvas = document.getElementById("id-canvas") as HTMLCanvasElement;
            let ctx = canvas.getContext("2d") as CanvasRenderingContext2D;
            ctx.textBaseline = "bottom";
            // 绘制背景
            ctx.fillStyle = "#e6ecfd";
            ctx.fillRect(0, 0, props.contentWidth, props.contentHeight);
            // 绘制文字
            for (let i = 0; i < props.identifyCode.length; i++) {
                drawText(ctx, props.identifyCode[i], i);
            }
            drawLine(ctx);
            drawDot(ctx);
        };

        const drawText = (ctx: CanvasRenderingContext2D, txt: string, i: number) => {
            ctx.fillStyle = randomColor(50, 160); // 随机生成字体颜色
            ctx.font = randomNum(props.fontSizeMin, props.fontSizeMax) + "px SimHei"; // 随机生成字体大小
            let x = (i + 1) * (props.contentWidth / (props.identifyCode.length + 1));
            let y = randomNum(props.fontSizeMax, props.contentHeight - 5);
            const deg = randomNum(-30, 30);
            // 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);
        };

        const drawLine = (ctx: any) => {
            // 绘制干扰线
            for (let i = 0; i < 4; i++) {
                ctx.strokeStyle = randomColor(100, 200);
                ctx.beginPath();
                ctx.moveTo(randomNum(0, props.contentWidth), randomNum(0, props.contentHeight));
                ctx.lineTo(randomNum(0, props.contentWidth), randomNum(0, props.contentHeight));
                ctx.stroke();
            }
        };

        const drawDot = (ctx: any) => {
            // 绘制干扰点
            for (let i = 0; i < 30; i++) {
                ctx.fillStyle = randomColor(0, 255);
                ctx.beginPath();
                ctx.arc(randomNum(0, props.contentWidth), randomNum(0, props.contentHeight), 1, 0, 2 * Math.PI);
                ctx.fill();
            }
        };

        onMounted(() => {
            drawPic();
        });

        watch(
            () => props.identifyCode,
            val => {
                console.log(val);
                drawPic();
            }
        );
</script>

<style lang="scss" scoped>
    .canvas-box {
        cursor: pointer;

        .id-canvas {
            height: 100%;
        }
    }
</style>