Vue uses mixins to implement compressed image code
This article mainly introduces Vue’s use of mixins to compress image code. Now I share it with you and give it a reference.
This article introduces the code of Vue using mixins to compress images, and shares it with everyone. The details are as follows:
Image compression
Create mixins image-compress. js
export default {
methods: {
/**
* 检查并压缩图片大小
*/
checkAndHandleCompression(file) {
return new Promise((resolve, reject) => {
this.imgBase64(file, (image, canvas) => {
let maxSize = 2 * 1024; // 2M (单位KB)
let fileSize = file.size / 1024; // 图片大小 (单位KB)
let uploadSrc, uploadFile;
if (fileSize > maxSize) { // 如果图片大小大于maxSize，进行压缩
uploadSrc = canvas.toDataURL(file.type, maxSize / fileSize);
uploadFile = this.convertBase64UrlToFile(uploadSrc, file.name); // 转成file文件
} else {
uploadSrc = image.src;
uploadFile = file;
}
let compressedSize = uploadFile.size / 1024;// 压缩后图片大小 (单位KB)
// 判断图片大小是否小于maxSize，如果大于则继续压缩至小于为止
if (compressedSize.toFixed(2) > maxSize) {
this.checkAndHandleUpload(uploadFile);
} else {
let fileOptions = {uploadSrc, uploadFile};
resolve(fileOptions);
}
});
});
},
/**
* 将图片转化为base64
*/
imgBase64(file, callback) {
// 看支持不支持FileReader
if (!file || !window.FileReader) return;
// 创建一个 Image 对象
let image = new Image();
// 绑定 load 事件处理器，加载完成后执行
image.onload = function () {
// 创建 canvas DOM 对象
let canvas = document.createElement('canvas');
// 返回一个用于在画布上绘图的环境, '2d' 指定了您想要在画布上绘制的类型
let ctx = canvas.getContext('2d');
// 如果高度超标 // 参数，最大高度
let MAX_HEIGHT = 3000;
if (image.height > MAX_HEIGHT) {
// 宽度等比例缩放 *=
image.width *= MAX_HEIGHT / image.height;
image.height = MAX_HEIGHT;
}
// 获取 canvas的 2d 环境对象,
// 可以理解Context是管理员，canvas是房子
ctx.clearRect(0, 0, canvas.width, canvas.height);
// 重置canvas宽高
canvas.width = image.width;
canvas.height = image.height;
// 将图像绘制到canvas上
ctx.drawImage(image, 0, 0, image.width, image.height);
callback(image, canvas);
};
if (/^image/.test(file.type)) {
// 创建一个reader
let reader = new FileReader();
// 将图片将转成 base64 格式
reader.readAsDataURL(file);
// 读取成功后的回调
reader.onload = function () {
// 设置src属性，浏览器会自动加载。
// 记住必须先绑定事件，才能设置src属性，否则会出同步问题。
image.src = this.result;
};
}
},
/**
* 把Base64转换成file文件
*/
convertBase64UrlToFile(dataurl, filename) {
let 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 File([u8arr], filename, {type: mime});
}
}
};example
<template>
...
</template>
<script>
import imageUploadMixins from '@/mixins/image-compress';
export default {
mixins: [imageUploadMixins],
...
methods:{
handleUploadImage(e){
let file = e.target.files[0];
this.checkAndHandleCompression(file).then( fileOptions => {
// let {uploadSrc, uploadFile} = fileOptions;
// 压缩完成使用 uploadSrc, uploadFile
...
});
}
}
...
}
</script>
<style>
...
</style>The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
Related articles:
vue data control view source code analysis
A brief discussion of React high-order components
vue-cli axios request method and cross-domain processing issues
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