Unable to add new canvas element with an existing

问题:

I am using 2 canvas elements. I am using one element as a main canvas element which has all the elements. I am generating a barcode in a separate canvas and would like to add it to the main canvas. Trying for a long time. Adding an example here fiddle

$(document).ready(function() {
 JsBarcode('#barcode', "1234", {
    width: 4,
    height: 20//displayValue: false
  });
  var bc = document.getElementById("barcode");
  var canvasx = bc.getContext("2d");
  var img1 = new Image();
  img1.src = bc.toDataURL("image/png");


  var c = document.getElementById("labelDesigner");
  var canvas = bc.getContext("2d");
  c.drawImage(img1);

});

I am using facric.js and JsBarcode. Thanks for the help in advance. If there is any other better way kindly suggest

回答1:

you can use fabric.Image.fromURL and pass the barcode canvas data as url.

DEMO

$(document).ready(function() {
  JsBarcode('#barcode', "1234", {
    width: 4,
    height: 20 //displayValue: false
  });
  var canvas = new fabric.Canvas("labelDesigner");
  var bc = document.getElementById("barcode");
  fabric.Image.fromURL(bc.toDataURL(),function(img){
   img.set({
      left: 0,
      top: 0
    })
   canvas.add(img);
  })
});

canvas[id^=c], div[id=output] {
    border: 1px solid red;
}

canvas[id=buffer] {
    border: 1px dotted green;
}

#output {
    padding: 15px;
}

#output img {
    border: 1px dotted blue;
}

<script src="https://rawgit.com/kangax/fabric.js/master/dist/fabric.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jsbarcode/3.9.0/JsBarcode.all.min.js"></script>
<canvas id="barcode"></canvas>
<canvas id="labelDesigner" width="410" height="200" style="border:1px solid #000000;margin-left:200px"></canvas>

回答2:

The drawImage-function can take another canvas as an argument, so you do not have to convert to an image inbetween. However, it always requires the x and y coordinates as the second and third parameters.

You had also swapped your c and canvas variables:

$(document).ready(function() {
 JsBarcode('#barcode', "1234", {
    width: 4,
    height: 20//displayValue: false
  });
  var bc = document.getElementById("barcode");
  var c = document.getElementById("labelDesigner");
  var context = c.getContext("2d");

  context.drawImage(bc, 0, 0);
});