js canvas實現滑塊驗證

<template>
 <div class="sliderContent">
 <div class="imgDev" :style="'width:' + width + 'px;'">
 <canvas :id="id" :width="width" :height="height"></canvas>
 <canvas
 class="slider"
 :id="id + 'sliderBlock'"
 :width="width"
 :height="height"
 :style="'left:' + sliderLeft + 'px;'"
 ></canvas>
 </div>
 <div class="moveSLider" :style="'width:' + width + 'px'">
 <div class="react" @mousedown.stop="moveBall($event)">
 <div
 class="yuan"
 :style="'left:' + (sliderLeft + 10) + 'px;'"
 ></div>
 </div>
 </div>
 </div>
</template>

<script>
export default {
 data() {
 return {
 width: 200,//盒子的寬度
 height: 200,//盒子的高度，當設置圖片原比例顯示的時候這個參數就不好使瞭
 id: new Date().getTime(),
 r: 9, //半圓的半徑
 w: 40, //滑塊的寬度
 imgOriginalScale: true, //圖片是否顯示原來比例
 sliderLeft: 0,//滑塊的初始位置
 rangeValue:4,//當滑塊到什麼范圍內算正確
 imgsrc:require("../assets/img/ver-2.png")//引入你想要的背景圖片
 };
 },
 mounted() {
 this.init();
 },
 methods: {
 init() {
 this.loadImage();
 },
 loadImage() {//加載圖片
 let mainDom = document.getElementById(this.id);
 let bg = mainDom.getContext("2d");
 let blockDom = document.getElementById(this.id + "sliderBlock");
 let block = blockDom.getContext("2d");
 let imgsrc = this.imgsrc;
 let img = document.createElement("img");
 img.style.objectFit = "scale-down";
 img.src = imgsrc;
 img.onload = () => {
 if (this.imgOriginalScale) {
 //根據圖片的尺寸變化計算一下圖片原來的比例
 mainDom.height = (img.height / img.width) * mainDom.width;
 blockDom.height = (img.height / img.width) * blockDom.width;
 }
 bg.drawImage(img, 0, 0, mainDom.width, mainDom.height);
 this.drawBlock(bg, mainDom.width, mainDom.height, "fill"); //繪制滑塊部分
 this.drawBlock(block, blockDom.width, blockDom.height, "clip", img); //繪制滑塊部分 這裡註意一定要先剪裁然後在繪制圖片(這裡圖片要傳進去不然沒有辦法控制)
 };
 },
 drawBlock(ctx, width, height, type, img) {//這裡是二合一函數，可以畫出陰影部分也切割出拼圖形狀的函數
 let { w, r, sliderLeft } = this;
 //這地方用隨機數每次顯示的位置都不同
 var x = this.random(30, width - w - r - 1); //這裡最大值為瞭不讓滑塊進入隱藏所以要減去滑塊的寬度 有個半圓所以要減去半圓位置
 var y = this.random(10, height - w - r - 1);
 if (type == "clip") {//這裡要保證在兩個東西要在同一個y值上
 x = sliderLeft;
 y = this.y;
 } else {
 this.x = x;
 this.y = y;
 }
 let PI = Math.PI;
 //繪制
 ctx.beginPath();
 //left
 ctx.moveTo(x, y);
 //top
 ctx.arc(x + (w + 5) / 2, y, r, -PI, 0, true);
 ctx.lineTo(x + w + 5, y);
 //right
 ctx.arc(x + w + 5, y + w / 2, r, 1.5 * PI, 0.5 * PI, false);
 ctx.lineTo(x + w + 5, y + w);
 //bottom
 ctx.arc(x + (w + 5) / 2, y + w, r, 0, PI, false);
 ctx.lineTo(x, y + w);
 ctx.arc(x, y + w / 2, r, 0.5 * PI, 1.5 * PI, true);
 ctx.lineTo(x, y);
 if (type == "clip") {
 ctx.shadowBlur = 10;
 ctx.shadowColor = "black";
 }
 ctx.lineWidth = 1;
 ctx.fillStyle = "rgba(0, 0, 0, 0.4)"; //設置背景顏色
 ctx.stroke();
 ctx[type]();
 if (img) {
 ctx.drawImage(img, -this.x, 0, width, height);
 }
 ctx.globalCompositeOperation = "xor";
 },
 random(min, max) {
 return parseInt(Math.floor(Math.random() * (max - min)) + min);
 },
 moveBall(e) {//當點擊小紅球的時候
 var oldx = e.pageX;
 document.onmousemove = (e) => {//這裡要綁定document對象不然你離開的他就不動瞭
 var x = e.pageX;
 if(this.sliderLeft+x-oldx<=0){//這裡判斷左邊界
 this.sliderLeft = 0;
 }else if(this.sliderLeft+x-oldx>=this.width-this.r*2-this.w){//這裡判斷右邊界
 this.sliderLeft = this.width-this.r*2-this.w;
 }else{
 this.sliderLeft += x - oldx;
 }
 oldx = x;
 };
 this.laveBall();
 },
 laveBall() {//鼠標松開的時候清空狀態
 document.onmouseup = ()=> {
 document.onmousemove = null;
 if(this.sliderLeft<(this.x+this.rangeValue)&&this.sliderLeft>(this.x-this.rangeValue)){
 console.log("恭喜你成功瞭")
 }else{//當沒用選中的時候重置一下滑塊的位置
 this.sliderLeft = 0;
 }
 };
 },
 },
};
</script>
<style lang="scss" scoped>
.moveSLider {
 position: relative;
 margin: 0 auto;
 height: 50px;
 .react {
 .yuan {
 position: absolute;
 left: 0;
 top: 50%;
 transform: translate(0, -50%);
 width: 30px;
 height: 30px;
 background-color: red;
 border-radius: 50%;
 cursor: pointer;
 }
 position: absolute;
 left: 0;
 top: 50%;
 transform: translate(0, -50%);
 width: 100%;
 height: 20px;
 background-color: rosybrown;
 }
}
.imgDev {
 position: relative;
 margin: 0 auto;
 .slider {
 position: absolute;
 left: 0;
 top: 0;
 background-color: transparent;
 }
}
</style>

drawBlock(ctx, width, height, type, img) {//這裡是二合一函數，可以畫出陰影部分也切割出拼圖形狀的函數
 let { w, r, sliderLeft } = this;//w寬度,r圓的半徑sliderLeft是滑塊的初始位置
 //這地方用隨機數每次顯示的位置都不同
 var x = this.random(30, width - w - r - 1); //這裡最大值為瞭不讓滑塊進入隱藏所以要減去滑塊的寬度 有個半圓所以要減去半圓位置
 var y = this.random(10, height - w - r - 1);
 if (type == "clip") {//這裡要保證在兩個東西要在同一個y值上
 x = sliderLeft;
 y = this.y;
 } else {
 this.x = x;
 this.y = y;
 }
 let PI = Math.PI;
 //繪制
 ctx.beginPath();
 //left
 ctx.moveTo(x, y);
 //top
 ctx.arc(x + (w + 5) / 2, y, r, -PI, 0, true);
 ctx.lineTo(x + w + 5, y);
 //right
 ctx.arc(x + w + 5, y + w / 2, r, 1.5 * PI, 0.5 * PI, false);
 ctx.lineTo(x + w + 5, y + w);
 //bottom
 ctx.arc(x + (w + 5) / 2, y + w, r, 0, PI, false);
 ctx.lineTo(x, y + w);
 ctx.arc(x, y + w / 2, r, 0.5 * PI, 1.5 * PI, true);
 ctx.lineTo(x, y);
 if (type == "clip") {
 ctx.shadowBlur = 10;
 ctx.shadowColor = "black";
 }
 ctx.lineWidth = 1;
 ctx.fillStyle = "rgba(0, 0, 0, 0.4)"; //設置背景顏色
 ctx.stroke();
 ctx[type]();
 if (img) {//這裡為什麼要在這裡加載圖片呢，因為這個高度是動態的必須計算完之後在放進去
 //還有個原因是你要先剪裁在加載圖片
 ctx.drawImage(img, -this.x, 0, width, height);
 }
},