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js實現上傳並壓縮圖片效果，js實現上傳圖片
本文執行個體為大家分享了js實現上傳並圖片壓縮的具體代碼，供大家參考，具體內容如下
代碼：
<!DOCTYPE html><html> <head> <meta charset="UTF-8"> <title></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 style="" 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("請確保檔案為映像類型"); return false; } var reader = new FileReader(); reader.readAsDataURL(file); reader.onload = function(e){ dealImage(this.result,{width:200},function(base){ document.getElementById('img').setAttribute('src',base) }); } } /** * 圖片壓縮，預設同比例壓縮 * @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 * 回呼函數有一個參數，base64的字串資料 */ function dealImage(path, obj, callback){ var img = new Image(); img.src = path; img.onload = function(){ var that = this; // 預設按比例壓縮 var w = that.width, h = that.height, scale = w / h; w = obj.width || w; h = obj.height || (w / scale); var quality = 0.7; // 預設圖片品質為0.7 //產生canvas var canvas = document.createElement('canvas'); var ctx = canvas.getContext('2d'); // 建立屬性節點 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); // 映像品質 if(obj.quality && obj.quality <= 1 && obj.quality > 0){ quality = obj.quality; } // quality值越小，所繪製出的映像越模糊 var base64 = canvas.toDataURL('image/jpeg', quality ); // 回呼函數返回base64的值 callback(base64); } } </script> </body></html>
以上就是本文的全部內容，希望對大家的學習有所協助，也希望大家多多支援幫客之家。
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