<!DOCTYPE html><html lang="en">
<head> <title></title> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1"></head>
<body> <script> window.onload = function () { var input = document.createElement('input'); input.type = 'file'; input.addEventListener('change', function () { var file = this.files[0]; var img = document.createElement('img'); img.src = window.URL.createObjectURL(file); img.onload = function () { var canvas = document.createElement('canvas'); var ctx = canvas.getContext('2d'); var MAX_WIDTH = 150; var MAX_HEIGHT = 200; var width = img.width; var height = img.height;
if (width > height) { if (width > MAX_WIDTH) { height *= MAX_WIDTH / width; width = MAX_WIDTH; } } else { if (height > MAX_HEIGHT) { width *= MAX_HEIGHT / height; height = MAX_HEIGHT; } }
canvas.width = width; canvas.height = height; ctx.drawImage(img, 0, 0, width, height); document.body.appendChild(canvas);
var btn = document.createElement('button'); btn.innerHTML = '上传'; document.body.appendChild(btn); btn.addEventListener('click', function() { /* toBlob的兼容性问题使用 https://github.com/blueimp/JavaScript-Canvas-to-Blob 这个库，就可以解决 */ canvas.toBlob(function(blob) { var form = new FormData(); form.append('file', blob); fetch('/api/upload', {method: 'POST', body: form}); }); }, false); };
// document.body.appendChild(img); 原始图片是不用展示出来的 }, false); document.body.appendChild(input); }; </script></body>
</html>
转载于:https://www.cnblogs.com/znj211985211/p/7047735.html
相关资源：数据结构—成绩单生成器