<script type="text/javascript">
  $(function () {
   var a = new tailorImg();
   a.iniData();
  });
  //
  var tailorImg=function()
  {
   this.iniData = function () {
    //画布
    this.can.id = "canvas";
    this.can.w = 400;
    this.can.h = 400;
    this.can.roundr = 7;
    this.can.roundrr = 3;
    this.can.curPointIndex = 0;
    this.can.imgBack.src = "gzf.png";
    this.can.canvas = document.getElementById(this.can.id).getContext("2d");
    //图片
    this.img.w = 400;
    this.img.h = 400;
    this.img.image.src = "flower.jpg";
    //加载事件：
    //初始化事件：
    var a = this;
    var p = a.can.pointList;
    $("#" + a.can.id).mousemove(function (e) {
     if (a.can.paint) {//是不是按下了鼠标 
      if (p.length > 0) {
       a.equalStartPoint(p[p.length - 1].pointx, p[p.length - 1].pointy);
      }
      a.roundIn(e.offsetX, e.offsetY);
     }
     //判断是否在直线上
     //光标移动到线的附近如果是闭合的需要重新划线，并画上新添加的点
     a.AddNewNode(e.offsetX, e.offsetY);
    });
    $("#" + a.can.id).mousedown(function (e) {
     a.can.paint = true;
     //点击判断是否需要在线上插入新的节点：
     if (a.can.tempPointList.length > 0) {
      a.can.pointList.splice(a.can.tempPointList[1].pointx, 0, new a.point(a.can.tempPointList[0].pointx, a.can.tempPointList[0].pointy));
      //清空临时数组
      a.can.tempPointList.length = 0;
     }
    });
    $("#" + a.can.id).mouseup(function (e) {
     //拖动结束
     a.can.paint = false;
     //拖动结束；
     if (a.can.juPull) {
      a.can.juPull = false;
      a.can.curPointIndex = 0;
      //验证抠图是否闭合：闭合，让结束点=开始点；添加标记
      a.equalStartPoint(p[p.length - 1].pointx, p[p.length - 1].pointy);
      //判断是否闭合：
      if (a.can.IsClose) {

      }
     }
     else {
      //如果闭合：禁止添加新的点；
      if (!a.can.IsClose) {//没有闭合
       p.push(new a.point(e.offsetX, e.offsetY));
       //验证抠图是否闭合：闭合，让结束点=开始点；添加标记
       a.equalStartPoint(p[p.length - 1].pointx, p[p.length - 1].pointy);
       //判断是否闭合：
       //重新画；
       if (p.length > 1) {
        a.drawLine(p[p.length - 2].pointx, p[p.length - 2].pointy, p[p.length - 1].pointx, p[p.length - 1].pointy);
        a.drawArc(p[p.length - 1].pointx, p[p.length - 1].pointy);
       } else {
        a.drawArc(p[p.length - 1].pointx, p[p.length - 1].pointy);
       }
      }
      else {
       //闭合
      }
     }
     //验证是否填充背景：
     if (a.can.IsClose) {
      a.fillBackColor();
      a.drawAllLine();
     }
    });
    $("#" + a.can.id).mouseleave(function (e) {
     a.can.paint = false;
    });
    //鼠标点击事件：
    $("#" + a.can.id).click(function (e) {
     //空
    });
   }
   this.point = function (x, y) {
    this.pointx = x;
    this.pointy = y;
   };
   //图片
   this.img = {
    image:new Image(),
    id: "",
    w:0,
    h:0
   };
   //画布；
   this.can = {
    canvas:new Object(),
    id: "",
    w: 0,
    h: 0,
    //坐标点集合
    pointList: new Array(),
    //临时存储坐标点
    tempPointList: new Array(),
    //圆点的触发半径：
    roundr: 7,
    //圆点的显示半径：
    roundrr: 7,
    //当前拖动点的索引值；
    curPointIndex : 0,
    //判断是否点击拖动
    paint : false,
    //判断是否点圆点拖动，并瞬间离开,是否拖动点；
    juPull : false,
    //判断是否闭合
    IsClose: false,
    imgBack: new Image()
    
   };
   //函数：
   //更新画线
   this.drawAllLine=function () {
    for (var i = 0; i < this.can.pointList.length - 1; i++) {
     //画线
     var p = this.can.pointList;
     this.drawLine(p[i].pointx, p[i].pointy, p[i + 1].pointx, p[i + 1].pointy);
     //画圈
     this.drawArc(p[i].pointx, p[i].pointy);
     if (i == this.can.pointList.length - 2) {
      this.drawArc(p[i+1].pointx, p[i+1].pointy);
     }
    }
   }
   //画线
   this.drawLine = function (startX, startY, endX, endY) {
    //var grd = this.can.canvas.createLinearGradient(0, 0,2,0); //坐标，长宽
    //grd.addColorStop(0, "black"); //起点颜色
    //grd.addColorStop(1, "white");
    //this.can.canvas.strokeStyle = grd;
    this.can.canvas.strokeStyle = "blue"
    this.can.canvas.lineWidth =1;
    this.can.canvas.moveTo(startX, startY);
    this.can.canvas.lineTo(endX, endY);
    this.can.canvas.stroke();
   }
   //画圈：
   this.drawArc=function(x, y) {
    this.can.canvas.fillStyle = "blue";
    this.can.canvas.beginPath();
    this.can.canvas.arc(x, y,this.can.roundrr, 360, Math.PI * 2, true);
    this.can.canvas.closePath();
    this.can.canvas.fill();
   }
   //光标移到线上画大圈：
   this.drawArcBig = function (x, y) {
    this.can.canvas.fillStyle = "blue";
    this.can.canvas.beginPath();
    this.can.canvas.arc(x, y, this.can.roundr+2, 360, Math.PI * 2, true);
    this.can.canvas.closePath();
    this.can.canvas.fill();
   }
   //渲染图片往画布上
   this.showImg=function() {
    this.img.image.onload = function () {
     this.can.canvas.drawImage(this.img.image, 0, 0, this.img.w,this.img.h);
    };
   }
   //填充背景色
   this.fillBackColor = function () {
    for (var i = 0; i <this.img.w; i += 96) {
     for (var j = 0; j <= this.img.h; j += 96) {
      this.can.canvas.drawImage(this.can.imgBack, i, j, 96, 96);
     }
    }
    this.can.canvas.globalCompositeOperation = "destination-out";
    this.can.canvas.beginPath();
    for (var i = 0; i <this.can.pointList.length; i++) {
     this.can.canvas.lineTo(this.can.pointList[i].pointx,this.can.pointList[i].pointy);
    }
    this.can.canvas.closePath();
    this.can.canvas.fill();
    this.can.canvas.globalCompositeOperation = "destination-over";
    this.drawAllLine();
   }
   //去掉pointlist最后一个坐标点：
   this.clearLastPoint=function () {
    this.can.pointList.pop();
    //重画：
    this.clearCan();
    this.drawAllLine();
   }
   //判断结束点是否与起始点重合；
   this.equalStartPoint = function (x,y) {
    var p = this.can.pointList;
    if (p.length > 1 && Math.abs((x - p[0].pointx) * (x - p[0].pointx)) + Math.abs((y - p[0].pointy) * (y - p[0].pointy)) <= this.can.roundr * this.can.roundr) {
     //如果闭合
     this.can.IsClose = true;
     p[p.length - 1].pointx = p[0].pointx;
     p[p.length - 1].pointy = p[0].pointy;
    }
    else {
     this.can.IsClose = false;
    }
   }
   //清空画布
   this.clearCan=function (){
    this.can.canvas.clearRect(0, 0, this.can.w, this.can.h);
   }
   //剪切区域
   this.CreateClipArea=function () {
    this.showImg();
    this.can.canvas.beginPath();
    for (var i = 0; i <this.can.pointList.length; i++) {
     this.can.canvas.lineTo(this.can.pointList[i].pointx,this.can.pointList[i].pointy);
    }
    this.can.canvas.closePath();
    this.can.canvas.clip();
   }
   //
   this.CreateClipImg=function()
   {

   }
   //判断鼠标点是不是在圆的内部：
   this.roundIn = function (x, y) {
    //刚开始拖动
    var p = this.can.pointList;
    if (!this.can.juPull) {
     for (var i = 0; i < p.length; i++) {

      if (Math.abs((x - p[i].pointx) * (x - p[i].pointx)) + Math.abs((y - p[i].pointy) * (y - p[i].pointy)) <= this.can.roundr * this.can.roundr) {
       //说明点击圆点拖动了；
       this.can.juPull = true;//拖动
       //
       this.can.curPointIndex = i;
       p[i].pointx = x;
       p[i].pointy = y;
       //重画：
       this.clearCan();
       //showImg();
       if (this.can.IsClose) {
        this.fillBackColor();
       }
       this.drawAllLine();
       return;
      }
     }
    }
    else {//拖动中
     p[this.can.curPointIndex].pointx = x;
     p[this.can.curPointIndex].pointy = y;
     //重画：
     this.clearCan();
     if (this.can.IsClose) {
      this.fillBackColor();
     }
     this.drawAllLine();
    }
   };

   //光标移到线上，临时数组添加新的节点：
   this.AddNewNode=function(newx, newy) {
    //如果闭合
    var ii=0;
    if (this.can.IsClose) {
     //判断光标点是否在线上：
     var p = this.can.pointList;
     for (var i = 0; i < p.length - 1; i++) {
      //计算a点和b点的斜率
      var k = (p[i + 1].pointy - p[i].pointy) / (p[i + 1].pointx - p[i].pointx);
      var b = p[i].pointy - k * p[i].pointx;
      //if (parseInt((p[i + 1].pointy - p[i].pointy) / (p[i + 1].pointx - p[i].pointx)) ==parseInt((p[i + 1].pointy - newy) / (p[i + 1].pointx - newx)) && newx*2-p[i+1].pointx-p[i].pointx<0 && newy*2-p[i+1].pointy-p[i].pointy<0) {
      // //如果在直线上
      // alert("在直线上");
      //}
      $("#txtone").val(parseInt(k * newx + b));
      $("#txttwo").val(parseInt(newy));
      if (parseInt(k * newx + b) == parseInt(newy) && (newx - p[i + 1].pointx) * (newx - p[i].pointx) <= 2 && (newy - p[i + 1].pointy) * (newy - p[i].pointy) <= 2) {
       //
       //parseInt(k * newx + b) == parseInt(newy)
       //添加临时点：
       this.can.tempPointList[0] = new this.point(newx, newy);//新的坐标点
       this.can.tempPointList[1] = new this.point(i+1, i+1);//需要往pointlist中插入新点的索引；
       i++;
       //alert();
       //光标移动到线的附近如果是闭合的需要重新划线，并画上新添加的点；
       if (this.can.tempPointList.length > 0) {
        //重画：
        this.clearCan();
        //showImg();
        if (this.can.IsClose) {
         this.fillBackColor();
        }
        this.drawAllLine();
        this.drawArcBig(this.can.tempPointList[0].pointx, this.can.tempPointList[0].pointy);
        return;
       }
       return;
      }
      else {
       // $("#Text1").val("");
      }
     }
     if (ii == 0) {
      if (this.can.tempPointList.length > 0) {
       //清空临时数组；
       this.can.tempPointList.length = 0;
       //重画：
       this.clearCan();
       //showImg();
       if (this.can.IsClose) {
        this.fillBackColor();
       }
       this.drawAllLine();
       //this.drawArc(this.can.tempPointList[0].pointx, this.can.tempPointList[0].pointy);
      }
     }
    }
    else {
     //防止计算误差引起的添加点，当闭合后，瞬间移动起始点，可能会插入一个点到临时数组，当再次执行时，
     //就会在非闭合情况下插入该点，所以，时刻监视：
     if (this.can.tempPointList.length > 0) {
      this.can.tempPointList.length = 0;
     }
    }
   }
   
  };

 </script>

<style type="text/css">
  .canvasDiv {
   position: relative;
   border: 1px solid red;
   height: 400px;
   width: 400px;
   top: 50px;
   left: 100px;
   z-index: 0;
  }

  img {
   width: 400px;
   height: 400px;
   z-index: 1;
   position: absolute;
  }

  #canvas {
   position: absolute;
   border: 1px solid green;
   z-index: 2;
  }
  .btnCollection {
   margin-left: 100px;
  }
 </style>

 <div class="canvasDiv">
    <img src="/UploadFiles/2021-04-02/flower.jpg">

 5.总结：
不足：当光标移动到线上时，判断一点是否在两点连成的直线上计算方法不正确，应该计算为一点是否在两点圆两条外切线所围成的矩形内；钢笔点应为替换为小的div方格比较合理，像下面的矩形抠图；（思路：将存取的点坐标集合和动态添加的小div方格建立对应关系当拖动小方格时，触发事件更新坐标点集合，并重新渲染）。
以上所述是小编给大家介绍的js+html5 canvas实现ps钢笔抠图详解整合，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！