如何使用nodejs将缓冲区转换为图像？

Question

这是我从 S3 存储桶获取图像的代码，但结果位于缓冲区中，我需要将其作为图像。请告诉我这样做

const AWS = require('aws-sdk')
const fs = require('fs')
const express = require('express')
const app = express()
app.get('/', (req, res) => {
  const s3 = new AWS.S3({
    accessKeyId: '################',
    secretAccessKey: '###############################',
    region: '###########'
  })

  const params = {
    Bucket: '#########',
    Key: '########'
  }
  s3.getObject(params, (err, rest) => {
    res.send(rest)
  })
})

app.listen(3000)

输出

{
  AcceptRanges: 'bytes',
  LastModified: 2020-06-29T10:42:17.000Z,
  ContentLength: 338844,
  ETag: '"769af0d798cd0486993711bc63340bd0"',
  ContentType: 'application/octet-stream',
  Metadata: {},
  Body: <Buffer ff d8 ff e0 00 10 4a 46 49 46 00 01 01 00 00 01 00 01 00 00 ff db 00 84 00 02 02 02 
  02 02 02 02 02 02 02 03 03 02 03 03 04 03 03 03 03 04 06 04 04 04 ... 338794 
  more bytes>
}

Answer 1

太长了；

/**
 * FINAL/WORKING SOLUTION
 */

// ...
app.get('/', (req, res) => {
  const s3 = new AWS.S3({
    accessKeyId: '-',
    secretAccessKey: '-',
    region: '-',
  });

  const params = {
    Bucket: '-',
    Key: '-',
  };

  s3.getObject(params, (err, rest) => {
    if (err) throw err;

    const b64 = Buffer.from(rest.Body).toString('base64');
    // CHANGE THIS IF THE IMAGE YOU ARE WORKING WITH IS .jpg OR WHATEVER
    const mimeType = 'image/png'; // e.g., image/png
    
    res.send(`<img src="data:${mimeType};base64,${b64}" />`);
  });
});
// ...

原答案

您将需要使用node“渲染”图像..也就是将响应作为<img />标签发送..

// ...
app.get('/', (req, res) => {
  const s3 = new AWS.S3({
    accessKeyId: '-',
    secretAccessKey: '-',
    region: '-',
  });

  const params = {
    Bucket: '-',
    Key: '-',
  };

  s3.getObject(params, (err, rest) => {
    if (err) throw err;

    const b64 = Buffer.from(rest).toString('base64');
    // NOTE: 
    // Because 'rest' appears to be a buffer, you might not 
    // need to do `Buffer.from(...)`,you may have to do something like:
    /** const b64 = rest.toString('base64'); **/
    const mimeType = 'image/png'; // e.g., image/png
    
    res.send(`<img src="data:${mimeType};base64,${b64}" />`);
  });
});
// ...

编辑1：

我相信这个问题与数据如何从 S3 返回给您有关。您可能需要执行类似rest.Body或的操作rest.body- 我不确定 S3 中的对象是什么样的。

话虽这么说，我将此图像本地保存为sample.png，并使用下面的代码加载它 - 它工作得很好。这证明该问题与 S3 将数据返回给您的方式有关。

const fs = require('fs');
const express = require('express');
const app = express();

app.get('/', (req, res) => {
  // Simulate getting data from S3 (aka data as buffer)
  const rest = Buffer.from(fs.readFileSync('./sample.png'));

  console.log('typeof rest = ' + typeof rest + '\r\n\r\n', rest);
  // typeof rest = object
  //
  // <Buffer 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 01 34 00 00 00 a4 08 03 00 00 00 2e 4e 22 5a 00 00 00 a2 50 4c 54 45 f7 f7 f7 cd 00 00 d1 00 00 ... 6360 more bytes>


  const b64 = rest.toString('base64');
  const mimeType = 'image/png'; // e.g., image/png

  res.send(`<img src="data:${mimeType};base64,${b64}" />`);
});

app.listen(3000);

编辑2：

看起来你需要这样做：

// ...
app.get('/', (req, res) => {
  const s3 = new AWS.S3({
    accessKeyId: '-',
    secretAccessKey: '-',
    region: '-',
  });

  const params = {
    Bucket: '-',
    Key: '-',
  };

  s3.getObject(params, (err, rest) => {
    if (err) throw err;

    const b64 = Buffer.from(rest.Body).toString('base64');
    // IF THE ABOVE LINE DOES NOT WORK, TRY THIS:
    // const b64 = rest.Body.toString('base64');

    // CHANGE THIS IF THE IMAGE YOU ARE WORKING WITH IS .jpg OR WHATEVER
    const mimeType = 'image/png'; // e.g., image/png
    
    res.send(`<img src="data:${mimeType};base64,${b64}" />`);
  });
});
// ...