Pasting directly to an HTML img element

Question

Re:question. Given that the following only applies to Firefox, is there a cross-browser solution? or is the Clipboard API too new (2020).

Original question:

---

In playing with the Clipboard API in Firefox. I was able to copy an image and paste it into a canvas.

const canvas = document.createElement("canvas");
canvas.setAttribute("contenteditable", "true")
document.body.appendChild(canvas);
canvas.style = "border:solid black 1px";
canvas.addEventListener("paste", element_paste(canvas, "canvas"));

function element_paste(element, type) {
  switch (type) {
    case "image":
      return function(e) {
        element.src = image_data_transfer(e.clipboardData || window.clipboardData);
      }
    case "canvas":
      return function(e) {
        const im = new Image();
        im.src = image_data_transfer(e.clipboardData || window.clipboardData);
        im.onload = () => {
          element.width = im.width;
          element.height = im.height;
          element.getContext("2d").drawImage(im, 0, 0);
          URL.revokeObjectURL(im.src);
          delete im;
        };
      }
    default:
      return function(e) {
        var p = (e.clipboardData || window.clipboardData).getData("text");
        var t = document.createTextNode(p);
        element.appendChild(t);
      }
  }
}

function image_data_transfer(e) {
  const p = e.items;
  try {
    return URL
      .createObjectURL(Array
        .apply(null, Array(p.length))
        .map((_, i) => p[i])
        .find(e => e.kind == "file" && /image/.test(e.type))
        .getAsFile()
      );
  } catch (e) {
    console.log(e);
    return "";
  }
}

This works exactly as expected for canvas. If canvas is changed to an img however; using "image" as the type in element_paste which would work if the html element would allow pasting to it.

I'm aware that I could "easily" overly a canvas over the image and it works exactly as expected. My issue with settling for that is ((I'm juggling another object only to serve as a workaround, I might as well use the canvas to save DOM mess.) (it's ugly.))

Is there any flag experimental or otherwise that would allow pasting directly to an img?

const img = document.createElement("img");
const image_paste = element_paste(img,"image");

document.body.appendChild(img);
img.setAttribute("contenteditable","true");
img.addEventListener("paste",image_paste);

img.style="border:solid black 1px;min-width:100px;min-height:100px";

The above is what I would like to work; below is a hack that does.

const canvas = document.createElement("canvas");
const img = document.createElement("img");
const image_paste = element_paste(img,"image");

document.body.appendChild(img);
document.body.appendChild(canvas);
canvas.setAttribute("contenteditable","true");
canvas.addEventListener("paste",image_paste);

canvas.style="border:solid black 1px;";
img.style="border:solid black 1px;min-width:100px;min-height:100px";

If there's a way for this to work without any script, even better!

sources:

• Paste an image from clipboard using JavaScript
• https://stackoverflow.com/a/10050831/5092123
• https://developer.mozilla.org
• firefox 77.0.1

Answer 1

This takes a couple different ideas and puts them together: Your clipboard data filter (modified slightly), and uses the FileReader class to turn it into a dataurl, which can be applied to an img object.

Interestingly though... it does not seem to work when the image object itself is selected.

const image = document.getElementById('img')
document.addEventListener('paste', convertToImage)

function convertToImage(e) {
  var blob = image_data_transfer(e.clipboardData)
  if (blob !== null) {
    var reader = new FileReader();
    reader.onload = function(event) {
      console.log(event.target.result);
      image.src = event.target.result
      alert('pasted!')
    }; // data url!
    reader.readAsDataURL(blob);
  } else {
    console.log("couldn't read image data from clipboard")
  }


}

function image_data_transfer(clipboardData) {
  const p = clipboardData.items;
  try {
    return Array
      .apply(null, Array(p.length))
      .map((_, i) => p[i])
      .find(e => e.kind == "file" && /image/.test(e.type))
      .getAsFile()
    // URL.createObjectURL();
  } catch (e) {
    console.log(e);
    return null;
  }
}

img{
  width: 300px;
  height: 300px;
  border: 1px solid;
  background: #ccc;
}

<div>
  Paste here!
</div>

<img id="img" src="" onpaste="convertToImage">