移动端利用H5实现压缩图片上传的功能

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 (!/\/(?:jpegpnggif)/i.test(file.type)) return;     var reader = new FileReader();     var li = document.createElement("li");    li.innerHTML = "<p class="progress"><span></span></p>";    $(".img-list").append($(li));     reader.onload = function () {     var result = this.result;     var img = new Image();     img.src = result;      //如果图片大小小于200kb，则直接上传     if (result.length <= maxsize) {      $(li).css("background-image", "url(" + result + ")");      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);       $(li).css("background-image", "url(" + data + ")");       upload(data, file.type, $(li));       img = null;     }     };     reader.readAsDataURL(file);   })  };

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 ArrayBuffer(text.length);  var ubuffer = new Uint8Array(buffer);  var pecent = 0 , loop = null;  for (var i = 0; i < text.length; i++) {   ubuffer[i] = text.charCodeAt(i);  }  var Builder = window.WebKitBlobBuilder window.MozBlobBuilder;  var blob;  if (Builder) {   var builder = new Builder();   builder.append(buffer);   blob = builder.getBlob(type);  } else {   blob = new window.Blob([buffer], {type: type});  }  var xhr = new XMLHttpRequest();  var formdata = new FormData();  formdata.append("imagefile", blob);  xhr.open("post", "/cupload");  xhr.onreadystatechange = function () {   if (xhr.readyState == 4 && xhr.status == 200) {    console.log("上传成功：" + xhr.responseText);    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("上传成功");    });    $(".pic-list").append("<a href="" + xhr.responseText + " rel="external nofollow" ">" + xhr.responseText + "<img  src="" + xhr.responseText + "" / alt="移动端利用H5实现压缩图片上传的功能" ></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); }