server/upload/index_2.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0" name="viewport">
  <title>移动端图片压缩上传demo</title>
  <style>
    *{margin: 0;padding: 0;}
    li{list-style-type: none;}
    a,input{outline: none;-webkit-tap-highlight-color:rgba(0,0,0,0);}
    #choose{display: none;}
    canvas{width: 100%;border: 1px solid #000000;}
    #upload{display: block;margin: 10px;height: 60px;text-align: center;line-height: 60px;border: 1px solid;border-radius: 5px;cursor: pointer;}
    .touch{background-color: #ddd;}
    .img-list{margin: 10px 5px;}
    .img-list li{position: relative;display: inline-block;width: 100px;height: 100px;margin: 5px 5px 20px 5px;border: 1px solid rgb(100,149,198);background: #fff no-repeat center;background-size: cover;}
    .progress{position: absolute;width: 100%;height: 20px;line-height: 20px;bottom: 0;left: 0;background-color:rgba(100,149,198,.5);}
    .progress span{display: block;width: 0;height: 100%;background-color:rgb(100,149,198);text-align: center;color: #FFF;font-size: 13px;}
    .size{position: absolute;width: 100%;height: 15px;line-height: 15px;bottom: -18px;text-align: center;font-size: 13px;color: #666;}
    .tips{display: block;text-align:center;font-size: 13px;margin: 10px;color: #999;}
    .pic-list{margin: 10px;line-height: 18px;font-size: 13px;}
    .pic-list a{display: block;margin: 10px 0;}
    .pic-list a img{vertical-align: middle;max-width: 30px;max-height: 30px;margin: -4px 0 0 10px;}
  </style>
</head>
<body>
<input type="file" id="choose" accept="image/*" multiple>
<ul class="img-list"></ul>
<a id="upload">上传图片</a>
<span class="tips">只允许上传jpg、png及gif</span>
<div class="pic-list">
  你上传的图片(图片有效期为1分钟)：
</div>

<script src="/public/jquery-2.1.1.min.js"></script>
<script>
  var filechooser = document.getElementById("choose");

  //    用于压缩图片的canvas
  var canvas = document.createElement("canvas");
  var ctx = canvas.getContext('2d');

  //    瓦片canvas
  var tCanvas = document.createElement("canvas");
  var tctx = tCanvas.getContext("2d");

  var maxsize = 100 * 1024;

  $("#upload").on("click", function() {
        filechooser.click();
      })
      .on("touchstart", function() {
        $(this).addClass("touch")
      })
      .on("touchend", function() {
        $(this).removeClass("touch")
      });

  filechooser.onchange = function() {
    if (!this.files.length) return;

    var files = Array.prototype.slice.call(this.files);

    if (files.length > 9) {
      alert("最多同时只可上传9张图片");
      return;
    }

    files.forEach(function(file, i) {
      if (!/\/(?:jpeg|png|gif)/i.test(file.type)) return;

      var reader = new FileReader();

      var li = document.createElement("li");

//          获取图片大小
      var size = file.size / 1024 > 1024 ? (~~(10 * file.size / 1024 / 1024)) / 10 + "MB" : ~~(file.size / 1024) + "KB";
      li.innerHTML = '<div class="progress"><span></span></div><div class="size">' + size + '</div>';
      $(".img-list").append($(li));

      reader.onload = function() {
        var result = this.result;
        var img = new Image();
        img.src = result;

        $(li).css("background-image", "url(" + result + ")");

        //如果图片大小小于100kb，则直接上传
        if (result.length <= maxsize) {
          img = null;

          upload(result, file.type, $(li));

          return;
        }

//      图片加载完毕之后进行压缩，然后上传
        if (img.complete) {
          callback();
        } else {
          img.onload = callback;
        }

        function callback() {
          var data = compress(img);

          upload(data, file.type, $(li));

          img = null;
        }

      };

      reader.readAsDataURL(file);
    })
  };

  //    使用canvas对大图片进行压缩
  function compress(img) {
    var initSize = img.src.length;
    var width = img.width;
    var height = img.height;

    //如果图片大于四百万像素，计算压缩比并将大小压至400万以下
    var ratio;
    if ((ratio = width * height / 4000000) > 1) {
      ratio = Math.sqrt(ratio);
      width /= ratio;
      height /= ratio;
    } else {
      ratio = 1;
    }

    canvas.width = width;
    canvas.height = height;

//        铺底色
    ctx.fillStyle = "#fff";
    ctx.fillRect(0, 0, canvas.width, canvas.height);

    //如果图片像素大于100万则使用瓦片绘制
    var count;
    if ((count = width * height / 1000000) > 1) {
      count = ~~(Math.sqrt(count) + 1); //计算要分成多少块瓦片

//            计算每块瓦片的宽和高
      var nw = ~~(width / count);
      var nh = ~~(height / count);

      tCanvas.width = nw;
      tCanvas.height = nh;

      for (var i = 0; i < count; i++) {
        for (var j = 0; j < count; j++) {
          tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh);

          ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);
        }
      }
    } else {
      ctx.drawImage(img, 0, 0, width, height);
    }

    //进行最小压缩
    var ndata = canvas.toDataURL('image/jpeg', 0.1);

    console.log('压缩前：' + initSize);
    console.log('压缩后：' + ndata.length);
    console.log('压缩率：' + ~~(100 * (initSize - ndata.length) / initSize) + "%");

    tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;

    return ndata;
  }

  //    图片上传，将base64的图片转成二进制对象，塞进formdata上传
  function upload(basestr, type, $li) {
    var text = window.atob(basestr.split(",")[1]);
    var buffer = new Uint8Array(text.length);
    var pecent = 0, loop = null;

    for (var i = 0; i < text.length; i++) {
      buffer[i] = text.charCodeAt(i);
    }

    var blob = getBlob([buffer], type);

    var xhr = new XMLHttpRequest();

    var formdata = getFormData();

    formdata.append('imagefile', blob);

    xhr.open('post', '/cupload');

    xhr.onreadystatechange = function() {
      if (xhr.readyState == 4 && xhr.status == 200) {
        var jsonData = JSON.parse(xhr.responseText);
        var imagedata = jsonData[0] || {};
        var text = imagedata.path ? '上传成功' : '上传失败';

        console.log(text + '：' + imagedata.path);

        clearInterval(loop);

        //当收到该消息时上传完毕
        $li.find(".progress span").animate({'width': "100%"}, pecent < 95 ? 200 : 0, function() {
          $(this).html(text);
        });

        if (!imagedata.path) return;

        $(".pic-list").append('<a href="' + imagedata.path + '">' + imagedata.name + '（' + imagedata.size + '）<img src="' + imagedata.path + '" /></a>');
      }
    };

    //数据发送进度，前50%展示该进度
    xhr.upload.addEventListener('progress', function(e) {
      if (loop) return;

      pecent = ~~(100 * e.loaded / e.total) / 2;
      $li.find(".progress span").css('width', pecent + "%");

      if (pecent == 50) {
        mockProgress();
      }
    }, false);

    //数据后50%用模拟进度
    function mockProgress() {
      if (loop) return;

      loop = setInterval(function() {
        pecent++;
        $li.find(".progress span").css('width', pecent + "%");

        if (pecent == 99) {
          clearInterval(loop);
        }
      }, 100)
    }

    xhr.send(formdata);
  }

  /**
   * 获取blob对象的兼容性写法
   * @param buffer
   * @param format
   * @returns {*}
   */
  function getBlob(buffer, format) {
    try {
      return new Blob(buffer, {type: format});
    } catch (e) {
      var bb = new (window.BlobBuilder || window.WebKitBlobBuilder || window.MSBlobBuilder);
      buffer.forEach(function(buf) {
        bb.append(buf);
      });
      return bb.getBlob(format);
    }
  }

  /**
   * 获取formdata
   */
  function getFormData() {
    var isNeedShim = ~navigator.userAgent.indexOf('Android')
        && ~navigator.vendor.indexOf('Google')
        && !~navigator.userAgent.indexOf('Chrome')
        && navigator.userAgent.match(/AppleWebKit\/(\d+)/).pop() <= 534;

    return isNeedShim ? new FormDataShim() : new FormData()
  }

  /**
   * formdata 补丁, 给不支持formdata上传blob的android机打补丁
   * @constructor
   */
  function FormDataShim() {
    console.warn('using formdata shim');

    var o = this,
        parts = [],
        boundary = Array(21).join('-') + (+new Date() * (1e16 * Math.random())).toString(36),
        oldSend = XMLHttpRequest.prototype.send;

    this.append = function(name, value, filename) {
      parts.push('--' + boundary + '\r\nContent-Disposition: form-data; name="' + name + '"');

      if (value instanceof Blob) {
        parts.push('; filename="' + (filename || 'blob') + '"\r\nContent-Type: ' + value.type + '\r\n\r\n');
        parts.push(value);
      }
      else {
        parts.push('\r\n\r\n' + value);
      }
      parts.push('\r\n');
    };

    // Override XHR send()
    XMLHttpRequest.prototype.send = function(val) {
      var fr,
          data,
          oXHR = this;

      if (val === o) {
        // Append the final boundary string
        parts.push('--' + boundary + '--\r\n');

        // Create the blob
        data = getBlob(parts);

        // Set up and read the blob into an array to be sent
        fr = new FileReader();
        fr.onload = function() {
          oldSend.call(oXHR, fr.result);
        };
        fr.onerror = function(err) {
          throw err;
        };
        fr.readAsArrayBuffer(data);

        // Set the multipart content type and boudary
        this.setRequestHeader('Content-Type', 'multipart/form-data; boundary=' + boundary);
        XMLHttpRequest.prototype.send = oldSend;
      }
      else {
        oldSend.call(this, val);
      }
    };
  }
</script>
</body>
</html>