javascript - 将图像元素放置在 Canvas 顶部

Question

我想将手的图片放在靠近脸部的黑色 Canvas 上。这可以吗？有没有办法确定图片的位置？

这是我的代码:

<script type="text/javascript" src="hand.jpg"></script>

<img src="hand.jpg" id="y" />
<canvas id="myCanvas" width="1600" height="1200"></canvas>
<script>
  var canvas;
  var canvasContext;

  window.onload = function() {
    canvas = document.getElementById('myCanvas');
    canvasContext = canvas.getContext('2d');
    canvasContext.fillStyle = 'black';

    canvasContext.fillRect(0, 0, canvas.width, canvas.height);
    //Draws a circle
    canvasContext.beginPath();
    canvasContext.fillStyle = 'yellow';
    canvasContext.arc(800, 400, 400, 400, 2 * Math.PI, true);
    canvasContext.fill();
    //draws head
    canvasContext.beginPath();
    canvasContext.fillStyle = 'white';
    canvasContext.arc(600, 200, 100, 100, 2 * Math.PI, true);
    canvasContext.fill();
    //draws eye1
    canvasContext.beginPath();
    canvasContext.fillStyle = 'white';
    canvasContext.arc(1000, 200, 100, 100, 2 * Math.PI, true);
    canvasContext.fill();
    //draws eye2
    canvasContext.fillStyle = 'black';
    canvasContext.fillRect(580, 175, 50, 50);
    //draws pupil1
    canvasContext.fillStyle = 'black';
    canvasContext.fillRect(980, 175, 50, 50);
    //draws pupil2
    canvasContext.fillStyle = 'black';
    canvasContext.fillRect(650, 550, 300, 6.5);
    //draws mouth

    function changingImg() {
      document.getElementById("y").src = "hand.jpg"
    }
  }
</script>

有办法解决这个问题吗？

Answer 1

我假设 <script type="text/javascript" src="hand.jpg"></script>这是一个小错误，它应该是 <script type="text/javascript" src="someFile.js"></script> 。但是，如果您要创建一个 JS 文件并像这样链接到它，您可能需要删除简单的 <script>标签如下。

继续，如果您想更改图像的大小，只需更改 .width和.height元素变量的属性。

例如:

var image = document.getElementById('y');

image.width = 1920; // Sets image's width to 1920
image.height = 1080; // Set's image's height to 1080

如果您想读取宽度和高度值，可以这样做:

var image = document.getElementById('y');
var imageWidth = image.width; // Image's width
var imageHeight = image.height; // Image's height