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javascript - 画布视图框窗口内的可点击对象或形状

问题描述

<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>

<style>
body {
  font-family: "Lato", sans-serif;
}

.sidenav {
  height: 100%;
  width: 0;
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  background-color: #111;
  overflow-x: hidden;
  transition: 0.5s;
  padding-top: 60px;
}

.sidenav a {
  padding: 8px 8px 8px 32px;
  text-decoration: none;
  font-size: 25px;
  color: #818181;
  display: block;
  transition: 0.3s;
}

.sidenav a:hover {
  color: #f1f1f1;
}

.sidenav .closebtn {
  position: absolute;
  top: 0;
  right: 25px;
  font-size: 36px;
  margin-left: 50px;
}

#main {
  transition: margin-left .5s;
  padding: 16px;
}

@media screen and (max-height: 450px) {
  .sidenav {padding-top: 15px;}
  .sidenav a {font-size: 18px;}
}
</style>
</head>
<body>

<div id="mySidenav" class="sidenav">
  <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a> 
  <a href="#">About</a>
  <a href="#">Services</a>
  <a href="#">Clients</a>
  <a href="#">Contact</a>
    
</div>
<div id="main">
  <span style="font-size:30px;cursor:pointer" onclick="openNav()">&#9776; Menu</span>
<canvas id="canvas" width="600" height="350" style="border:2px solid #d3d3d3;">></canvas>
</div>

<script>

var zoomIntensity = 0.1;
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
var width = 90;
var height = 50;
var scale = 1;
var originx = 0;
var originy = 0;
var visibleWidth = width;
var visibleHeight = height;


var c = document.getElementById("canvas");
var ctx = c.getContext("2d");

function draw(){

    context.fillStyle = "white";
    context.fillRect(originx,originy,1000/scale,800/scale);

    context.fillStyle = "blue";
    context.fillRect(170,50,50,50);
    context.fillStyle = "white";
    context.fillText('click here',175,70);   
}

setInterval(draw, 1000/60);
canvas.onwheel = function (event){
    event.preventDefault();
    var mousex = event.clientX - canvas.offsetLeft;
    var mousey = event.clientY - canvas.offsetTop;
    var wheel = event.deltaY < 0 ? 1 : -1;
    var zoom = Math.exp(wheel*zoomIntensity);
    
    context.translate(originx, originy);
    originx -= mousex/(scale*zoom) - mousex/scale;
    originy -= mousey/(scale*zoom) - mousey/scale;
    context.scale(zoom, zoom);
    context.translate(-originx, -originy);
    scale *= zoom;
    visibleWidth = width / scale;
    visibleHeight = height / scale;
}
function openNav() {
  document.getElementById("mySidenav").style.width = "200px";
  document.getElementById("main").style.marginLeft = "200px";
}

function closeNav() {
  document.getElementById("mySidenav").style.width = "0";
  document.getElementById("main").style.marginLeft= "0";
}
</script>

</body>
</html>

是否可以在画布框架或视图框上制作可点击的形状或对象，即使我放大或缩小，因为我看到的所有示例都只是一个固定的可点击位置。例如，当我放大谷歌地图位置时，我可以点击更多对象。是否可以在画布框架或视图框上制作可点击的形状或对象，即使我放大或缩小，因为我看到的所有示例都只是一个固定的可点击位置。例如，当我放大谷歌地图位置时，我可以点击更多对象。

标签： javascripthtmljquerycanvasclickable

解决方案

您必须考虑两个空间，实际画布空间和翻译空间。这意味着您需要转换鼠标坐标才能知道对象实际位于空间中的哪个位置，并将其映射回画布坐标，这样您就可以知道您是否正在单击它。这是通过跟踪var originx您context.translate(originx, originy)在空间。

我在不使用翻译功能的情况下重写了代码，方法是制作我自己的翻译功能，使您能够在画布空间和对象空间之间进行翻译，以便在对象上注册点击事件，而不管平移或放大位置如何。

此功能还具有单击平移功能，因此您可以单击对象屏幕并将其拖动到要放置对象的任何位置。

/*jshint esversion: 8 */

(function() {
  const canvas = document.querySelector("canvas");
  const context = canvas.getContext("2d");
  let canvasWidth = 600;
  let canvasHeight = 600;
  let offset = {
    x: 0,
    y: 0
  };
  let pan = {
    x: 0,
    y: 0
  };
  var zoomIntensity = 0.1;
  let scale = 1;
  let mouse = {
    x: 0,
    y: 0
  };
  let dragging = false;
  let square;

  let shapes = [{
      x: 170,
      y: 50,
      w: 50,
      h: 50,
      color: "blue"
    },
    {
      x: 85,
      y: 25,
      w: 50,
      h: 50,
      color: "red"
    },
    {
      x: 50,
      y: 100,
      w: 50,
      h: 50,
      color: "green"
    },
  ];

  function init() {
    canvas.width = canvasWidth;
    canvas.height = canvasHeight;

    renderCanvas();
  }

  function drawSquare(x, y, width, height, color) {
    context.fillStyle = color;
    context.fillRect(x, y, width, height);
  }

  function objectsToCanvasScreen(x, y) {
    const canvasScreenX = Math.floor((x - offset.x) * scale);
    const canvasScreenY = Math.floor((y - offset.y) * scale);

    return {
      x: canvasScreenX,
      y: canvasScreenY
    };
  }

  function canvasToObjectsScreen(x, y) {
    return {
      x: x / scale + offset.x,
      y: y / scale + offset.y
    };
  }

  function renderCanvas() {
    context.clearRect(0, 0, canvas.width, canvas.height);

    shapes.forEach(({
      x,
      y,
      w,
      h,
      color
    }, index) => {
      const {
        x: csx,
        y: csy
      } = objectsToCanvasScreen(x, y);
      shapes[index]._x = csx;
      shapes[index]._y = csy;
      shapes[index]._w = w * scale;
      shapes[index]._h = h * scale;
      drawSquare(csx, csy, w * scale, h * scale, color);
    });

  }

  canvas.onwheel = function(e) {
    const zoom = Math.exp((e.deltaY < 0 ? 1 : -1) * zoomIntensity);
    const beforeZoom = canvasToObjectsScreen(mouse.x, mouse.y);
    scale *= zoom;
    const afterZoom = canvasToObjectsScreen(mouse.x, mouse.y);
    offset.x += beforeZoom.x - afterZoom.x;
    offset.y += beforeZoom.y - afterZoom.y;

    renderCanvas();
  };
  canvas.onmousedown = function(e) {
    if (e.button === 0) {
      pan.x = mouse.x;
      pan.y = mouse.y;
      dragging = true;
    }
  };
  canvas.onmouseup = (e) => (dragging = false);
  canvas.onmousemove = function(e) {
    mouse.x = e.offsetX;
    mouse.y = e.offsetY;
    if (dragging) {
      offset.x -= (mouse.x - pan.x) / scale;
      offset.y -= (mouse.y - pan.y) / scale;

      pan.x = mouse.x;
      pan.y = mouse.y;
      renderCanvas();
    }
  };
  canvas.onclick = function(e) {
    shapes.forEach(({
      _x,
      _y,
      _w,
      _h,
      color
    }) => {
      const {
        x: mousex,
        y: mousey
      } = canvasToObjectsScreen(mouse.x, mouse.y);
      const {
        x: squarex,
        y: squarey
      } = canvasToObjectsScreen(_x, _y);
      if (
        mousex >= squarex &&
        mousex <= _w / scale + squarex &&
        mousey >= squarey &&
        mousey <= _h / scale + squarey
      ) {
        alert(`${color} clicked!`);
      }
    });

  };

  init();
})();
body {
  font-family: "Lato", sans-serif;
}

#canvas {
  background: #E1BC8B;
}
<body>
  <div id="main">
    <canvas id="canvas" width="300" height="350"></canvas>
  </div>
</body>

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