具體代碼如下所示：
<!DOCTYPE html><html><head> <meta charset="UTF-8"> <title>前端壓縮上傳圖片</title> <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script></head><body> <input type="file" id="picFile" onchange="readFile(this)" /> <img id="img" src="" alt="" /> <script> function readFile(obj) { var file = obj.files[0]; //判斷類型是不是圖片 if (!/image///w+/.test(file.type)) { alert("請確保文件為圖像類型"); return false; } var reader = new FileReader(); reader.readAsDataURL(file); reader.onload = function(e) { dealImage(this.result, { quality: 0.5 }, function(base) { //調用 var blob = dataURLtoBlob(base); var newFile = new File([blob], file.name, { type: file.type }); console.log(newFile) let r = new FileReader(); //本地預覽 r.onload = function() { $('#img').attr("src", r.result);; } r.readAsDataURL(newFile); //Base64 // upload(newFile); }); } } //將base64轉換為blob function dataURLtoBlob(dataurl) { var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1], bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n); while (n--) { u8arr[n] = bstr.charCodeAt(n); } return new Blob([u8arr], { type: mime }); } function upload(file) { var that = this; // 創建form對象 let param = new FormData(); // 通過append向form對象添加數據 param.append('img', file); // 文件大小 param.append('size', file.size); for (var n in that.params) { param.append(n, that.params[n]); } // 創建ajax var xhr = new XMLHttpRequest(); xhr.onload = function() { console.log(xhr.responseText) } xhr.open("POST", "yourapi", true); // 發送表單數據 xhr.send(param); } /** * 圖片壓縮，默認同比例壓縮 * @param {Object} path * pc端傳入的路徑可以為相對路徑，但是在移動端上必須傳入的路徑是照相圖片儲存的絕對路徑 * @param {Object} obj * obj 對象 有 width， height， quality(0-1) * @param {Object} callback * 回調函數有一個參數，base64的字符串數據 */ function dealImage(path, obj, callback) { var img = new Image(); img.src = path; img.onload = function() { var that = this; // 默認按比例壓縮 var w = that.width, h = that.height, scale = w / h; w = obj.width || w; h = obj.height || (w / scale); var quality = obj.quality || 0.7; // 默認圖片質量為0.7 //生成canvas var canvas = document.createElement('canvas'); var ctx = canvas.getContext('2d'); // 創建屬性節點 var anw = document.createAttribute("width"); anw.nodeValue = w; var anh = document.createAttribute("height"); anh.nodeValue = h; canvas.setAttributeNode(anw); canvas.setAttributeNode(anh); ctx.drawImage(that, 0, 0, w, h); // 圖像質量 if (obj.quality && obj.quality <= 1 && obj.quality > 0) { quality = obj.quality; } // quality值越小，所繪制出的圖像越模糊 var base64 = canvas.toDataURL('image/jpeg', quality); // 回調函數返回base64的值 callback(base64); } } </script></body></html>
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