小猿圈web前端讲师为了大家更好的学习前端知识决定每天分享一个web前端案例，希望对你与学习前端的你有所帮助，今天分享的是移动端Vue+Vant的Uploader实现上传、压缩、旋转图片等功能的详细介绍。
面向百度开发
html
<van-uploader :after-read="onRead" accept="image/*">
<img src="./icon_input_add.png" />
</van-uploader>
js
data() {
return {
files: {
name: "",
type: ""
},
headerImage: null,
picValue: null,
upImgUrl,
}
},
// 组件方法 获取 流
async onRead(file) {
// console.log(file);
// console.log(file.file);
this.files.name = file.file.name; // 获取文件名
this.files.type = file.file.type; // 获取类型
this.picValue = file.file; // 文件流
this.imgPreview(this.picValue);
},
// 处理图片
imgPreview(file) {
let self = this;
let Orientation;
//去获取拍照时的信息，解决拍出来的照片旋转问题
Exif.getData(file, function () {
Orientation = Exif.getTag(this, "Orientation");
});
// 看支持不支持FileReader
if (!file || !window.FileReader) return;
if (/^image/.test(file.type)) {
// 创建一个reader
let reader = new FileReader();
// 将图片2将转成 base64 格式
reader.readAsDataURL(file);
// 读取成功后的回调
reader.onloadend = function () {
// console.log(this.result);
let result = this.result;
let img = new Image();
img.src = result;
//判断图片是否大于500K,是就直接上传，反之压缩图片
if (this.result.length <= 500 * 1024) {
self.headerImage = this.result;
self.postImg();
} else {
img.onload = function () {
let data = self.compress(img, Orientation);
self.headerImage = data;
self.postImg();
};
}
};
}
},
// 压缩图片
compress(img, Orientation) {
let canvas = document.createElement("canvas");
let ctx = canvas.getContext("2d");
//瓦片canvas
let tCanvas = document.createElement("canvas");
let tctx = tCanvas.getContext("2d");
// let initSize = img.src.length;
let width = img.width;
let height = img.height;
//如果图片大于四百万像素，计算压缩比并将大小压至400万以下
let ratio;
if ((ratio = (width * height) / 4000000) > 1) {
// console.log("大于400万像素");
ratio = Math.sqrt(ratio);
width /= ratio;
height /= ratio;
} else {
ratio = 1;
}
canvas.width = width;
canvas.height = height;
// 铺底色
ctx.fillStyle = "#fff";
ctx.fillRect(0, 0, canvas.width, canvas.height);
//如果图片像素大于100万则使用瓦片绘制
let count;
if ((count = (width * height) / 1000000) > 1) {
// console.log("超过100W像素");
count = ~~(Math.sqrt(count) + 1); //计算要分成多少块瓦片
// 计算每块瓦片的宽和高
let nw = ~~(width / count);
let nh = ~~(height / count);
tCanvas.width = nw;
tCanvas.height = nh;
for (let i = 0; i < count; i++) {
for (let j = 0; j < count; j++) {
tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh);
ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);
}
}
} else {
ctx.drawImage(img, 0, 0, width, height);
}
//修复ios上传图片的时候 被旋转的问题
if (Orientation != "" && Orientation != 1) {
switch (Orientation) {
case 6: //需要顺时针（向左）90度旋转
this.rotateImg(img, "left", canvas);
break;
case 8: //需要逆时针（向右）90度旋转
this.rotateImg(img, "right", canvas);
break;
case 3: //需要180度旋转
this.rotateImg(img, "right", canvas); //转两次
this.rotateImg(img, "right", canvas);
break;
}
}
//进行最小压缩
let ndata = canvas.toDataURL("image/jpeg", 0.1);
tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;
return ndata;
},
// 旋转图片
rotateImg(img, direction, canvas) {
//最小与最大旋转方向，图片旋转4次后回到原方向
const min_step = 0;
const max_step = 3;
if (img == null) return;
//img的高度和宽度不能在img元素隐藏后获取，否则会出错
let height = img.height;
let width = img.width;
let step = 2;
if (step == null) {
step = min_step;
}
if (direction == "right") {
step++;
//旋转到原位置，即超过最大值
step > max_step && (step = min_step);
} else {
step--;
step < min_step && (step = max_step);
}
//旋转角度以弧度值为参数
let degree = (step * 90 * Math.PI) / 180;
let ctx = canvas.getContext("2d");
switch (step) {
case 0:
canvas.width = width;
canvas.height = height;
ctx.drawImage(img, 0, 0);
break;
case 1:
canvas.width = height;
canvas.height = width;
ctx.rotate(degree);
ctx.drawImage(img, 0, -height);
break;
case 2:
canvas.width = width;
canvas.height = height;
ctx.rotate(degree);
ctx.drawImage(img, -width, -height);
break;
case 3:
canvas.width = height;
canvas.height = width;
ctx.rotate(degree);
ctx.drawImage(img, -width, 0);
break;
}
},
//将base64转换为文件
dataURLtoFile(dataurl) {
var arr = dataurl.split(","),
bstr = atob(arr[1]),
n = bstr.length,
u8arr = new Uint8Array(n);
while (n--) {
u8arr[n] = bstr.charCodeAt(n);
}
return new File([u8arr], this.files.name, {
type: this.files.type
});
},
//这里写接口
async postImg() {
let file = this.dataURLtoFile(this.headerImage);
let formData = new window.FormData();
formData.append("file", file);
toast_loding(this, "图片上传中···");
try {
let res = await util.ajax.post(this.upImgUrl, formData, {
headers: {
"Content-Type": "multipart/form-data"
}
});
} catch (e) {
console.log(e);
}
}
以上就是小猿圈web前端讲师给大家分享的移动端Vue+Vant的Uploader实现上传、压缩、旋转图片等功能的详细介绍，希望对你有所帮助web前端自学②群：738735873，想要了解更多内容的小伙伴可以到小猿圈官网进行学习，里面有最新最全面的课程内容等你来学习，而且小猿圈上所有的视频都是免费的学习的。
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