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js移动端图片压缩上传功能

时间:2021-07-01 10:21:17 帮助过:18人阅读

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脚本之家。

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