重點代碼解析

1.圖片預(yù)覽

html代碼塊

  <div align="center" style="padding-top:10px;">
    <input type="file" name="file" id="doc" style="width:150px;"   onchange="javascript:setImagePreview();">
  </div>

js代碼塊

    //下面用于圖片上傳預(yù)覽功能
    function setImagePreview(avalue) {
      var docObj = document.getElementById("doc");
      console.log(docObj.files)
      var imgObjPreview = document.getElementById("image");
      if (docObj.files && docObj.files[0]) {
        火狐下，直接設(shè)img屬性
        imgObjPreview.style.display = 'block';
        imgObjPreview.style.maxWidth = '960px';
        imgObjPreview.style.height = '400px';
        //imgObjPreview.src = docObj.files[0].getAsDataURL();
        // 取絕對路徑的getAsDataURL
        //火狐7以上版本不能用上面的getAsDataURL()方式獲取，需要一下方式
        imgObjPreview.src = window.URL.createObjectURL(docObj.files[0]);
      } else {
        //IE下，使用濾鏡
        docObj.select();
        var imgSrc = document.selection.createRange().text;
        var localImagId = document.getElementById("localImag");
        //必須設(shè)置初始大小
        localImagId.style.maxWidth = "960px";
        localImagId.style.height = 'auto';
        //圖片異常的捕捉，防止用戶修改后綴來偽造圖片
        try {
          localImagId.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";     localImagId.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
        } catch (e) {
          alert("您上傳的圖片格式不正確，請重新選擇!");
          return false;
        }
        imgObjPreview.style.display = 'none';
        document.selection.empty();
      }
      return true;
    }

2.canvas toDataURL 轉(zhuǎn)Blob文件

function dataURLtoBlob(dataurl) {
        var arr = dataurl.split(','),
          mime = arr[0].match(/:(.*?);/)[1],
          bstr = atob(arr[1]),
          n = bstr.length,
          u8arr = new Uint8Array(n);
        while (n--) {
          u8arr[n] = bstr.charCodeAt(n);
        }
        return new Blob([u8arr], {
          type: mime
        });
      }
    });

3.發(fā)送Aiax請求

 button2.onclick = function () {
      var fd = new FormData();
      fd.append("image", blob, "image.png");
      var xhr = new XMLHttpRequest();
      xhr.open('POST', '/personal/upload', true);
      xhr.send(fd);
    }

所有代碼

demo地址：demo