JQ图片压缩上传

css

* {
				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;
			}

html

<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>

js

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);
					}
				};
			}

温馨提示：记得引入JQ哦