js移动端图片压缩上传功能

移动端图片压缩上传功能如何实现？

做移动端开发的时候，form里面的file后台经常获取不到，用foemdata也拿不到

找到了一个formdata的脚本

<!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 + '" rel="external nofollow" >' + 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>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。

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