update: I manually changed cnv.width = this.width to 120 and it kind of works. I also found that the image has rendered size and intrinsic size. Width is 35 for rendered size and 40 for intrinsic size, so I guess this could be the reason.

I am trying to use selenium to get captcha image from a web page. Here is what I have tried based on examples from this site

def get_ver_code(driver):
    img = driver.find_element(By.XPATH, '//*[@id="imgCode"]')
    img = driver.execute_async_script("""
        var ele = arguments[0], callback = arguments[1];
        ele.addEventListener('load', function fn(){
          ele.removeEventListener('load', fn, false);
          var cnv = document.createElement('canvas');
          cnv.width = this.width; cnv.height = this.height;
          cnv.getContext('2d').drawImage(this, 0, 0);
          callback(cnv.toDataURL('image/jpeg').substring(22));
        }, false);
        ele.dispatchEvent(new Event('load'));
        """, img)
    with open(r"captcha.jpg", 'wb') as f:
        f.write(base64.b64decode(img))
        
    base64_decoded = base64.b64decode(img)
    img = Image.open(io.BytesIO(base64_decoded))
    img = np.array(img)
    return img

This is almost fine, except that the images downloaded are always slightly cropped on the right side. A lot of times it doesn't affect the digits, but sometimes it does. For example:

How can I fix this?