JavaScript上传前获取文件大小，图像宽度和高度

  • Z时代
  • 2024-01-10
  • 分类：问答

在使用jQuery或JavaScript上传到我的网站之前，如何获取文件大小，图像高度和宽度？

回答：

带有信息数据预览的多张图像上传

使用

图片来源将是代表Blob对象的URL

<img src="blob:null/026cceb9-edr4-4281-babb-b56cbf759a3d">

const EL_browse  = document.getElementById('browse');
const EL_preview = document.getElementById('preview');
const readImage  = file => {
  if ( !(/^image\/(png|jpe?g|gif)$/).test(file.type) )
    return EL_preview.insertAdjacentHTML('beforeend', `Unsupported format ${file.type}: ${file.name}<br>`);
  const img = new Image();
  img.addEventListener('load', () => {
    EL_preview.appendChild(img);
    EL_preview.insertAdjacentHTML('beforeend', `<div>${file.name} ${img.width}×${img.height} ${file.type} ${Math.round(file.size/1024)}KB<div>`);
    window.URL.revokeObjectURL(img.src); // Free some memory
  });
  img.src = window.URL.createObjectURL(file);
}
EL_browse.addEventListener('change', ev => {
  EL_preview.innerHTML = ''; // Remove old images and data
  const files = ev.target.files;
  if (!files || !files[0]) return alert('File upload not supported');
  [...files].forEach( readImage );
});
#preview img { max-height: 100px; }
<input id="browse" type="file" multiple>
<div id="preview"></div>

使用FileReader API的

如果您需要图像源作为长Base64编码的数据字符串

<img src="data:image/png;base64,iVBORw0KGg... ...lF/++TkSuQmCC=">

const EL_browse  = document.getElementById('browse');
const EL_preview = document.getElementById('preview');
const readImage = file => {
  if ( !(/^image\/(png|jpe?g|gif)$/).test(file.type) )
    return EL_preview.insertAdjacentHTML('beforeend', `<div>Unsupported format ${file.type}: ${file.name}</div>`);
  const reader = new FileReader();
  reader.addEventListener('load', () => {
    const img  = new Image();
    img.addEventListener('load', () => {
      EL_preview.appendChild(img);
      EL_preview.insertAdjacentHTML('beforeend', `<div>${file.name} ${img.width}×${img.height} ${file.type} ${Math.round(file.size/1024)}KB</div>`);
    });
    img.src = reader.result;
  });
  reader.readAsDataURL(file);
};
EL_browse.addEventListener('change', ev => {
  EL_preview.innerHTML = ''; // Clear Preview
  const files = ev.target.files;
  if (!files || !files[0]) return alert('File upload not supported');
  [...files].forEach( readImage );
});
#preview img { max-height: 100px; }
<input id="browse" type="file"  multiple>
<div id="preview"></div>

以上是 JavaScript上传前获取文件大小，图像宽度和高度 的全部内容， 来源链接： utcz.com/qa/406665.html

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