Question

我想使用HTML5的canvas标记和JavaScript在页面中裁剪多个图像。问题是页面只显示其中一个图像。

我该怎么办？我试过的代码如下：

<canvas id="myCanvas" width="300" height="300"></canvas>
<canvas id="myCanvas" width="300" height="300"></canvas>
<canvas id="myCanvas" width="300" height="300"></canvas>
<script>
  var canvas = document.getElementById('myCanvas');
  var context = canvas.getContext('2d');
  var imageObj = new Image();

  imageObj.onload = function() {
    // draw cropped image
    var sourceX = 0;
    var sourceY = 0;
    var sourceWidth = 200;
    var sourceHeight = 150;
    var destWidth = sourceWidth;
    var destHeight = sourceHeight;
    var destX = canvas.width / 2 - destWidth / 2;
    var destY = canvas.height / 2 - destHeight / 2;

    context.drawImage(imageObj, sourceX, sourceY, sourceWidth, sourceHeight, destX, destY, destWidth, destHeight);
  };

imageObj.src ='http://static.adzerk.net/Advertisers/3478c54721cd466fb6f7d3afe16e97d4.gif';

</script>

小提琴：http://jsfiddle.net/soheilyou/54VTh/

Answer 1

就像Some Guy所说的那样，每个画布都使用相同的id - 这是禁忌。尝试给每个人一个唯一的id或使用一个类。

然后，这只是逐个抓取元素的问题 - 你可以do with JavaScript或者更容易使用jQuery（下面）。

查看this updated Fiddle或查看此JavaScript代码段：

var canvases = $('.myCanvas');
$(canvases).each(function () {
    var canvas = $(this).get(0); //Grab the canvas node from the jQuery container.
    var context = canvas.getContext('2d');
    var imageObj = new Image();

    imageObj.onload = function () {
        var sourceX = 0;
        var sourceY = 0;
        var sourceWidth = 200;
        var sourceHeight = 150;
        var destWidth = sourceWidth;
        var destHeight = sourceHeight;
        var destX = canvas.width / 2 - destWidth / 2;
        var destY = canvas.height / 2 - destHeight / 2;

        context.drawImage(imageObj, sourceX, sourceY, 
                          sourceWidth, sourceHeight, destX, 
                          destY, destWidth, destHeight);
    };

    imageObj.src = 'path/to/your/image.png';
});

一次使用几个画布

1 个答案: