calculated gradient in html2canvas doesn't work properly

I am trying to take a screenshot of a page that has images overlayed by linear-gradient with the help of html2canvas. The height of the image varies but the width is fixed to 210px so, i need to use calc to calculate the positons of the gradient, which is not rendering in the way it looks on the screen.

Example with static values: https://jsfiddle.net/vpj3bz7s/1/

.linearGradient {
  height: 200px;
  width: 210px;
  background-image: linear-gradient(to top left,
      yellow 0%,
      yellow 80px,
      red 80px,
      red 110px,
      yellow 110px,
      yellow 100%);
}
html2canvas(document.body).then(function(canvas) {
    document.body.appendChild(canvas);
  }
);
<div class="linearGradient"></div>

Example with calc values: https://jsfiddle.net/dk309pf6/2/

.linearGradient {
  height: 200px;
  width: 210px;
  background-image: linear-gradient(to top left,
      yellow 0%,
      yellow calc(50% - 10px),
      red calc(50% - 10px),
      red calc(50% + 10px),
      yellow calc(50% + 10px),
      yellow 100%);
}

html2canvas(document.body).then(function(canvas) {
    document.body.appendChild(canvas);
  }
);
<div class="linearGradient"></div>

Edit: Actual image overlayed on gradient looks like this:

The way it looks like in a screenshot is this:

The JS fiddle with my actual code is as follows (But the screenshot is a little different from my original one)

https://jsfiddle.net/nrfjh8m3/1/

Here is a different idea to obtain the same gradient. There is a ton of ways but the below is the only one that worked with html2canvas:

body {
  margin: 0px;
}

.linearGradient {
  height: 200px;
  width: 210px;
  background-color:red;
  overflow:hidden;
   position:relative;
}
.linearGradient::before,
.linearGradient::after {
   content:"";
   position:absolute;
   top:0;
   left:0;
   bottom:0;
   right:0;
   background-repeat:no-repeat;
}
.linearGradient::before {
  background:linear-gradient(to bottom right,yellow 49%, transparent 50%);
  bottom:10px;
  right:10px;
}
.linearGradient::after {
  background:linear-gradient(to top left,yellow 49%, transparent 50%);
  top:10px;
  left:10px;
}

<div class="linearGradient"></div>

Working code with html2canvas:

https://jsfiddle.net/k79ybnup/1/