h5图片压缩上传

1、图片上传过慢，图片进行压缩上传

<div class="form-item item-first">
    <input type="file" id="choose" accept="image/*" multiple>
    <ul class="img-list">
      <li class="tmp-img"></li>
    </ul>
    <div id="upload">上传图片</div>
</div>

.item-first{display:flex;align-items:flex-end;}
.img-list li{position:relative;display:block;margin:0 auto;margin:0 auto;width:90px;height:120px;background-color:#fff;background-position:center center;background-repeat:no-repeat;}
.progress{position:absolute;bottom:0;left:0;width:100%;height:20px;background-color:rgba(254,61,73,.5);line-height:20px;}
.progress span{display:block;width:0;height:100%;background-color:#fe3d49;color:#fff;text-align:center;font-size:13px;}
.size{position:absolute;bottom:-18px;width:100%;height:15px;color:#666;text-align:center;font-size:13px;line-height:15px;}
.tips{display:block;margin:10px;color:#999;text-align:center;font-size:13px;}
.pic-list{margin:10px;font-size:13px;line-height:18px;}
.pic-list a{display:block;margin:10px 0;}
.pic-list a img{margin:-4px 0 0 10px;max-width:30px;max-height:30px;vertical-align:middle;}
.tmp-img{margin:0 auto;width:90px;height:120px;background-color:#fff;background-image:url(../images/upload_img.png);background-size:67px 64px;}

<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>';
      $(".img-list").html($(li));
      $('.img-list li').attr("style","background-image: url(../images/loading_big.gif);background-size: 60px 60px");
      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) {
    console.log(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('file', blob);
    xhr.open('post', '上传图片地址url');
    xhr.onreadystatechange = function() {
      
      if (xhr.readyState == 4 && xhr.status == 200) {
        var jsonData = JSON.parse(xhr.responseText);
        var imagedata = jsonData.data || {};
        var text = imagedata.url ? '上传成功' : '上传失败';
        console.log(text + '：' + imagedata.url);
        $('.img-list li').attr("style","background-image: url("+imagedata.url+");background-size: 100% 100%");
        $('#upload').attr('data-picId',imagedata.url);
        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 + '
Content-Disposition: form-data; name="' + name + '"');
      if (value instanceof Blob) {
        parts.push('; filename="' + (filename || 'blob') + '"
Content-Type: ' + value.type + '

');
        parts.push(value);
      }
      else {
        parts.push('

' + value);
      }
      parts.push('
');
    };
    // Override XHR send()
    XMLHttpRequest.prototype.send = function(val) {
      var fr,
          data,
          oXHR = this;
      if (val === o) {
        // Append the final boundary string
        parts.push('--' + boundary + '--
');
        // 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>