javascript - 在image1上重叠image2

我们在站点中显示image1，如下所示:

现在，我们提供了一个上传image2的选项，我们想要上传的image2应该与here这样的现有image1重叠。

但是现在当我们上传image2时，image1在image2上重叠了。

var canvas = new fabric.Canvas('canvas');
document.getElementById('file').addEventListener("change", function (e) {
  var file = e.target.files[0];
  var reader = new FileReader();
  reader.onload = function (f) {
    var data = f.target.result;
    fabric.Image.fromURL(data, function (img) {
     // var oImg = img.set({left: 0, top: 0, angle: 00,width:100, height:100}).scale(0.9);
	  var oImg = img.set({left: 0, top: 0, angle: 00, width: canvas.getWidth(), height: canvas.getHeight()});
      canvas.add(oImg).renderAll();
      var a = canvas.setActiveObject(oImg);
      var dataURL = canvas.toDataURL({format: 'png', quality: 0.8});
    });
  };
  reader.readAsDataURL(file);
});


var img = new Image();
img.onload = function() {
  //draw after loading
  var canvas = document.getElementById('case_canvas');
  var ctx = canvas.getContext("2d");
  ctx.drawImage(img, 0, 0, img.naturalWidth, img.naturalHeight);
}

img.src = "http://i.stack.imgur.com/xgNw7.png";
//^^ this will start loading the image

/*.canvas-container {
  background: url("http://i.stack.imgur.com/xgNw7.png") no-repeat fixed center;

  }
  */

 .canvas-container {
 width: 300px; height: 500px;  position: relative; -webkit-user-select: none; top:900px;
 }

 #canvas
 {
  border: 1px solid black;
  top:500px;
}

#file
{
	position:relative;top:900px;
}

.lower-canvas

{
	position: absolute; width: 300px; height: 500px; bottom:400px; left: 0px; -webkit-user-select: none;
}

.upper-canvas {
position: absolute; width: 300px; height: 500px; left: 0px; top: 0px; -webkit-user-select: none; cursor: default;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://rawgit.com/kangax/fabric.js/master/dist/fabric.min.js"></script>
<input  type="file" id="file"><br />
<canvas id="canvas" width="450" height="450"></canvas>

<div class="canvas-container">
<canvas id="case_canvas" width="300" height="500" class="lower-canvas" ></canvas>
<canvas class="upper-canvas " width="300" height="500" ></canvas>
</div>

单击Run code Snippet后，请向下滚动以查看结果。

最佳答案

加

#case_canvas {
     z-index:-1
}

给你的CSS。这会将 Canvas 和案例的轮廓放置在所有上传的图片后面。但是，请确保上传的图片尺寸正确。例如，通过.scale(x)或将宽度设置为 Canvas 宽度的某个比例，因为现在是这样，它将覆盖整个 Canvas (如果足够大的话)，并且根本看不到这种情况。

Image2

javascript - 在image1上重叠image2