标签：canvas const 压缩 maxW maxH base64Image image 图片
图片压缩
设置1M以上图片压缩
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
</head>
<body>
<input type="file" id="upload" />
<script>
const upload = document.getElementById("upload");
const ACCEPT = ["image/jpg", "image/png", "image/jpeg","image/webp"];
const MAXSIZE = 1024 * 1024;
function convetImageToBase64(file, callback) {
let reader = new FileReader();
reader.addEventListener("load", function (e) {
const base64Image = e.target.result;
callback && callback(base64Image);
reader = null;
});
reader.readAsDataURL(file);
}
function compress(base64Image, callback) {
console.log(base64Image, "初始的base64");
let maxW = 1024;
let maxH = 1024;
const image = new Image();
image.addEventListener("load", function (e) {
let ratio; //图片的压缩比
let needCompress = false; //是否压缩
if (maxW < image.naturalWidth) {
needCompress = true;
ratio = image.naturalWidth / maxW;
maxH = image.naturalHeight / ratio;
}
if (maxH < image.naturalHeight) {
needCompress = true;
ratio = image.naturalHeight / maxH;
maxW = image.naturalWidth / ratio;
}
if (!needCompress) {
maxW = image.naturalWidth;
maxH = image.naturalHeight;
}
const canvas = document.createElement("canvas");
canvas.setAttribute("id", "__compress__");
canvas.width = maxW;
canvas.height = maxH;
canvas.style.visibility = "visibile";
document.body.appendChild(canvas);
const ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, maxW, maxH);
ctx.drawImage(image, 0, 0, maxW, maxH);
const compressImage = canvas.toDataURL("image/jpeg", 0.9);
callback && callback(compressImage);
const _image = new Image();
_image.src = compressImage;
document.body.appendChild(_image);
canvas.remove();
});
image.src = base64Image;
document.body.appendChild(image);
}
function uploadToServer(compressImage) {
console.log("上传", compressImage);
}
upload.addEventListener("change", (e) => {
const [file] = e.target.files;
if (!file) {
return;
}
const { type: fileType, size: fileSize } = file;
if (!ACCEPT.includes(fileType)) {
alert("不支持[" + fileType + "]类型");
upload.value = "";
return;
}
if (fileSize > MAXSIZE) {
alert(`文件超出1MB`);
}
//图片压缩
convetImageToBase64(file, (base64Image) =>
compress(base64Image, uploadToServer)
);
});
</script>
</body>
</html>
标签：canvas,const,压缩,maxW,maxH,base64Image,image,图片 来源： https://www.cnblogs.com/lht1132950411/p/16299901.html
本站声明： 1. iCode9 技术分享网（下文简称本站）提供的所有内容，仅供技术学习、探讨和分享； 2. 关于本站的所有留言、评论、转载及引用，纯属内容发起人的个人观点，与本站观点和立场无关； 3. 关于本站的所有言论和文字，纯属内容发起人的个人观点，与本站观点和立场无关； 4. 本站文章均是网友提供，不完全保证技术分享内容的完整性、准确性、时效性、风险性和版权归属；如您发现该文章侵犯了您的权益，可联系我们第一时间进行删除； 5. 本站为非盈利性的个人网站，所有内容不会用来进行牟利，也不会利用任何形式的广告来间接获益，纯粹是为了广大技术爱好者提供技术内容和技术思想的分享性交流网站。