隐藏页面顶部的空白区域

Hide the empty space present on top of the page

本文关键字：空白 区域 顶部 隐藏      更新时间：2023-09-26

如果您单击"运行代码段"或选中此处，您可以看到开头有很多空白，一旦我们向下滚动，就只能看到图像。

我想把那些空的地方藏起来。

我试过position:relative; top: some px; bottom: some px;，但对我不起作用。

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 = "https://i.stack.imgur.com/xgNw7.png";
//^^ this will start loading the image
/*.canvas-container {
  background: url("https://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>

您必须将画布容器的顶部位置从900更改为更低的值。

请参阅以下片段

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 = "https://i.stack.imgur.com/xgNw7.png";
//^^ this will start loading the image
/*.canvas-container {
  background: url("https://i.stack.imgur.com/xgNw7.png") no-repeat fixed center;
  }
  */
 
 .canvas-container {
 width: 300px; height: 500px;  position: relative; -webkit-user-select: none; top:0px;
 }
 
 #canvas
 {
  border: 1px solid black;
  top:500px;
}
#file
{
	position:relative;top:0px;
}
.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>

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