Sending blob image from Angular to ExpressJS - node.js

Question

I'm trying to send a blob image, but I'm getting Error: Unexpected end of form using multer with Serverless Framework.
From console.log
My understanding is I have to append it to FormData before sending it in the body, but I haven't been able to get backend to accept file without crashing
uploadImage(imageData: File) {
console.log('IMAGE DATA', imageData);
let formData = new FormData();
formData.append('file', imageData, 'file.png');
let headers = new HttpHeaders();
headers.append('Content-Type', 'multipart/form-data');
headers.append('Accept', 'application/json');
let options = { headers: headers };
const api = environment.slsLocal + '/add-image';
const req = new HttpRequest('PUT', api, formData, options);
return this.http.request(req);
}
backend
const multerMemoryStorage = multer.memoryStorage();
const multerUploadInMemory = multer({
storage: multerMemoryStorage
});
router.put(
'/add-image',
multerUploadInMemory.single('file'),
async (req, res: Response) => {
try {
if (!req.file || !req.file.buffer) {
throw new Error('File or buffer not found');
}
console.log(`Upload Successful!`);
res.send({
message: 'file uploaded'
});
} catch (e) {
console.error(`ERROR: ${e.message}`);
res.status(500).send({
message: e.message
});
}
console.log(`Upload Successful!`);
return res.status(200).json({ test: 'success' });
}
);
app.ts
import cors from 'cors';
import express from 'express';
import routers from './routes';
const app = express();
import bodyParser from 'body-parser';
app.use(cors({ maxAge: 43200 }));
app.use(
express.json({
verify: (req: any, res: express.Response, buf: Buffer) => {
req.rawBody = buf;
}
})
);
app.use('/appRoutes', routers.appRouter);
app.use(
bodyParser.urlencoded({
extended: true // also tried extended:false
})
);
export default app;
From my understanding with serverless framework I have to install
npm i serverless-apigw-binary
and add
apigwBinary:
types: #list of mime-types
- 'image/png'
to the custom section of the serverless template yaml file.
The end goal is not to save to storage like S3, but to send the image to discord.
What am I missing? I appreciate any help!

Answer 1

I recently encountered something similar in a react native app. I was trying to send a local file to an api but it wasn't working. turns out you need to convert the blob file into a base64 string before sending it. What I had in my app, took in a local file path, converted that into a blob, went through a blobToBase64 function, and then I called the api with that string. That ended up working for me.
I have this code snippet to help you but this is tsx so I don't know if it'll work for angular.
function blobToBase64(blob: Blob) {
return new Promise((resolve, reject) => {
const reader = new FileReader();
reader.onerror = reject;
reader.onload = () => {
resolve(reader.result as string);
};
reader.readAsDataURL(blob);
});
}
Hope this helps!

Answer 2

You can convert your Blob to a File using
new File([blob], "filename")
and then you should be able pass that file to your existing uploadImage method.

Answer 3

Looks like you are passing Blob instead of File based on your console.log(). So you should convert Blob to a File before calling the server. You can change your frontend code like this:
uploadImage(imageData: File) {
// Convert Blob to File
const file = new File([imageData], "file_name", { type: imageData.type });
let formData = new FormData();
formData.append('file', file, 'file.png');
const api = environment.slsLocal + '/add-image';
return this.http.put(api, formData);
}
Note: For more info about converting Blob to File, you can check this StackOverflow question.

Answer 4

The thing that got it working for me was this article.
There might be something different about using Express through Serverless Framework so things like mutler and express-fileupload might not work. Or could be because it's an AWS Lambda function. I don't know this for sure though. I just know I never got it working. This article was the only thing that worked for Serverless Framework + Express.
I also had to install version 0.0.3 of busboy ie npm i busboy#0.0.3. The newer version didn't work for busboy. Newer version was saying Busboy is not a constructor
Since I'm sending the file to discord and not S3 like this article does, I had to tweak the parser.event part in this part of the article for the handler.ts
export const uploadImageRoute = async (
event: any,
context: Context
): Promise<ProxyResult> => {
const parsedEvent: any = await parser(event);
await sendImageToDiscord(parsedEvent.body.file);
const response = {
statusCode: 200,
body: JSON.stringify('file sent successfully')
};
return response;
};
comes in as a Buffer which I was able to send as a file like this
const fs = require('fs-extra');
const cwd = process.cwd();
const { Webhook } = require('discord-webhook-node');
const webhook = new Webhook('<discord-webhook-url>');
export async function sendImageToDiscord(arrayBuffer) {
var buffer = Buffer.from(arrayBuffer, 'base64');
const newFileName = 'nodejs.png';
await fs.writeFile(`./${newFileName}`, buffer, 'utf-8').then(() => {
webhook.sendFile(`${cwd}/${newFileName}`);
});
}
});
I hope this helps someone!