How to customize photo albums in uniapp

With the popularity of mobile devices, photo albums have become an indispensable part of mobile phone users' lives. In application development, how to customize photo albums? This article will introduce you to how to customize photo albums in uniapp.

1. Basic use of photo albums in uniapp

There are two basic ways to use photo albums in uniapp:

1. Configure permissions in the manifest.json file, use The uni.chooseImage() method calls the photo album:

//manifest.json
"android": {
  "permissions": [
    "android.permission.READ_EXTERNAL_STORAGE",
    "android.permission.WRITE_EXTERNAL_STORAGE"
  ]
}
//业务逻辑
uni.chooseImage({
  count: 1, //选择图片数量，选填，默认9
  success: function(res) {
    console.log(res)
  }
});

2. Add the 3525558f8f338d4ea90ebf22e5cde2bc tag in the template and obtain the image through the fileChange event:

<template>
  <view>
    <input type="file" accept="image/*" @change="fileChange"/>
  </view>
</template>

<script>
export default {
  data() {
    return {};
  },
  methods: {
    fileChange(e) {
      console.log(e.target.files[0]);
    }
  }
};
</script>

The above two methods are basic ways to use photo albums, but in some business scenarios it may be necessary to implement some customized functions.

2. Customization function of photo album in uniapp

1. Control the scaling ratio of album pictures

The default scaling ratio of uniapp is 1:1, there are Sometimes we need to control the zoom ratio when selecting an image. This can be achieved by setting the value of the compress option in the count and chooseImage hook functions:

uni.chooseImage({
  count: 1,
  compress: {
    //设置缩放比例为16:9
    width: 640,
    height: 360,
    compressType: 'image/jpeg',
    quality: 90
  },
  success: function(res) {
    console.log(res)
  }
});

2. Sort by shooting time

In some photo album applications, pictures are sorted according to the time they were taken. Uniapp sorts by file name by default, so you need to implement the logic of sorting by shooting time yourself.

First you need to get the shooting time of the picture. You can use the exif.js library to read the shooting time in the exif information of the picture.

import ExifReader from 'exif-js';

const file = files[0];
const reader = new FileReader();
reader.readAsArrayBuffer(file);
reader.onload = () => {
  //解析exif信息获取拍摄时间
  const tags = ExifReader.load(reader.result);
  const date = tags?.DateTimeOriginal?.value;
};

Next, add the obtained shooting time to an array, and bind the image index and shooting time together:

const arr = [];
for (let i = 0; i < res.tempFilePaths.length; i++) {
  const filePath = res.tempFilePaths[i];
  const file = files[i];
  const reader = new FileReader();
  reader.readAsArrayBuffer(file);
  reader.onload = () => {
    //解析exif信息获取拍摄时间
    const tags = ExifReader.load(reader.result);
    const date = tags?.DateTimeOriginal?.value;
    //绑定图片索引和拍摄时间
    arr.push({ index: i, date });
    if (arr.length === res.tempFilePaths.length) {
      //按拍摄时间排序
      const newArr = arr.sort((a, b) => new Date(b.date) - new Date(a.date));
      const tempFilePaths = newArr.map((item) => res.tempFilePaths[item.index]);
      console.log(tempFilePaths);
    }
  };
}

This way you can sort by shooting time Functional.

3. Select multiple pictures and stitch them into one picture

In some specific scenarios, it is necessary to allow users to select multiple pictures and stitch them into one picture. At this time, you need to use canvas to stitch together multiple pictures.

First, you need to get multiple pictures selected by the user and draw them on the canvas:

let canvas = document.createElement('canvas');
let ctx = canvas.getContext('2d');
//设置canvas的大小，假设最多允许选取4张图片，宽度为窗口的一半，高度为宽度的0.6倍
canvas.width = document.documentElement.clientWidth / 2;
canvas.height = canvas.width * 0.6;
let x = 0;
let y = 0;
for (let i = 0; i < this.tempFilePaths.length; i++) {
  let img = new Image();
  img.src = this.tempFilePaths[i];
  //等待所有图片都加载完成
  img.onload = () => {
    //绘制图片
    ctx.drawImage(img, x, y, canvas.width / 2, canvas.height / 2);
    //根据图片数量分别计算下一张图片在canvas中的位置
    if (i === 0) {
      x += canvas.width / 2;
    } else if (i === 1) {
      x -= canvas.width / 2;
      y += canvas.height / 2;
    } else if (i === 2) {
      x += canvas.width / 2;
    }
    //当所有图片都绘制完毕后，将canvas转换为图片
    if (i === this.tempFilePaths.length - 1) {
      let tempFilePath = canvas.toDataURL();
    }
  };
}

With the above code, you can splice the selected pictures into one picture.

4. Summary

Through the introduction of this article, I believe you can already understand how to customize photo albums in uniapp, including controlling the zoom ratio of pictures, sorting by shooting time, multiple selection of pictures and stitched together into one picture.

For developing mobile applications, photo albums are a very common function. Mastering the customization skills of photo albums can better improve the user experience of the application. I hope this article can be helpful to everyone.

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