canvas.drawImage 裁剪图像

Question

Hello I have the following image:

with size 750x554

I load the iamge into a img tag, of the following way:

 <input type="file" accept="image/*"
        onchange="document.getElementById('character').src = window.URL.createObjectURL(this.files[0]);">

      <img id="character" alt="your image" width="100" height="100" />

And in order to convert this image into a base64 I use canvas with the following code:

  let canvas = document.createElement("canvas");

  canvas.width = img.width
  canvas.height = img.height

  let ctx = canvas.getContext("2d");
  ctx.drawImage(img, 0, 0);

  let dataURL = canvas.toDataURL("image/png");

But the result that I get is a cropped image as you can see here

How can solve this, and get the image in base64?

Thanks.

Answer 1

you need to set the canvas to the size of the image and you need to wait for the image to actually load before trying to draw it.

 document.querySelector('input').addEventListener('change', function() { const url = window.URL.createObjectURL(this.files[0]); const img = document.getElementById('character'); img.addEventListener('load', function() { let canvas = document.createElement("canvas"); canvas.width = img.naturalWidth; canvas.height = img.naturalHeight; let ctx = canvas.getContext("2d"); ctx.drawImage(img, 0, 0); let dataURL = canvas.toDataURL("image/png"); // show image const i = new Image(); i.src = dataURL; document.body.appendChild(i); }); img.src = url; });

 <input type="file" accept="image/*"> <img id="character" alt="your image" width="100" height="100" />

Answer 2

I think here problem is with your image tag since you have specified the image's width and height as 100

<img id="character" alt="your image" width="100" height="100" />

So instead of this just give the actual height and width to image tag.

Happy Coding !!!