Rendering image from API response in NextJS - just downloads base64 file

Question

I am working on a new project and learning ReactJS. I have saved an image in base64 to a MySQL database and I am now trying to do a GET request so the image is shown in the browser instead of it being downloaded, however, although it attempts to download the file, the file is just a file containing the base64 string instead of an actual image.

The file in the database looks like the below (only a snippet of the base64)

data:image/png;base64,iVBORw0KGgoAAAA

The API to fetch the image is as below:

export default async function handler(req : NextApiRequest, res : NextApiResponse) {
    const prisma = new PrismaClient()

    if (req.method === "GET")
    {
        const {image_id} = req.query;
        const image = await prisma.images.findFirst({
            where: {
                imageId: parseInt(image_id)
            }
        });
        const decoded = Buffer.from(image.content).toString("base64");
        console.log(decoded)
        res.status(200).send(decoded);
    }
    else
    {
        res.status(405).json(returnAPIErrorObject(405, "Method not supported by API endpoint"));
    }
}

I've modified the next.config.js to provide a custom header response which contains the below:

module.exports = {
    async headers() {
        return [
            {
                source: '/api/images/:image_id',
                headers: [
                    {
                        key: 'Content-Type',
                        value: 'image/png:Base64'
                    }
                ]
            }
        ]
    }
}

As mentioned, when I go to the URL http://localhost:3000/api/images/4 (4 being the image id) it downloads a file that contains the base64 string that is in the database, instead of showing the image in the browser.

UPDATE

Based on the link in the comment from @sean w it now attempts to display the image but instead of showing the actual picture, it just shows a blank window with a white square as shown in the screenshot below.

My code now looks like the following:

        const {image_id} = req.query;
        const image = await prisma.images.findFirst({
            where: {
                imageId: parseInt(image_id)
            }
        });

        const decoded = Buffer.from(image.content, 'base64').toString();

        let imageContent = decoded.replace(/^data:image\/png;base64,/, '');

        console.log(decoded);

        res.writeHead(200, {
            'Content-Type': 'image/png',
            'Content-Length': imageContent.length
        });
        res.end(imageContent);

Below is a screenshot showing what actually gets rendered on the page instead of my actual image.

Answer 1

I've figured out the issue, instead of creating the buffer from the database which I think looks like Prisma as the column was a blob was giving me a buffer anyway. , I first extract the base64 string from the DB and remove the data:image/png;base64 from the string and then create a buffer from that string and send that for the response:

const {image_id} = req.query;
        const image = await prisma.images.findFirst({
            where: {
                imageId: parseInt(image_id)
            }
        });

        const decoded = image.content.toString().replace("data:image/png;base64,", "");
        const imageResp = new Buffer(decoded, "base64");

        res.writeHead(200, {
            'Content-Type': 'image/png',
            'Content-Length': imageResp.length
        });
        res.end(imageResp);