how to embed an image in a JSON response

Question

I'm using Jimp to read in a JSON string that looks like this:

As you can see the image node is a base64-encoded JPEG.

I'm able to succesfully convert it to a TIFF and save it:

  Jimp.read(Buffer.from(inputImage, "base64"), function(err, image) {
    image.getBuffer(Jimp.MIME_TIFF, function(error, tiff) {
    context.bindings.outputBlob = tiff
    ...}

However, when I attempted to embed the tiff inside of a JSON object, the TIFF gets all garbled up:

  const response = {
    image: tiff.toString('base64'),
    correlation: correlation
  };

  context.bindings.outputBlob = response;

Here's the full code:

const Jimp = require("jimp");

module.exports = function(context, myBlob) {
  const correlation = context.bindings.inputBlob.correlation;
  const inputImage = context.bindings.inputBlob.image;
  const imageName = context.bindings.inputBlob.imageName;

  context.log(
    correlation + "Attempting to convert this image to a tiff: " + imageName
  );
  Jimp.read(Buffer.from(inputImage, "base64"), function(err, image) {
    image.getBuffer(Jimp.MIME_TIFF, function(error, tiff) {
      const response = {
        image: tiff.toString('base64'),
        correlation: correlation
      };

      context.bindings.outputBlob = response;
      context.log(
        correlation + "Succesfully converted " + imageName + " to tiff."
      );
      context.done();
    });
  });
};

How do we embed the tiff inside of a JSON payload?

If this output is non-negotiable, how would I render the tiff from the saved payload?

Jimp calls UTIF, which reads any kind of tiff, but only seems to write uncompressed RGBA tiffs. In general, decompressing and recompressing an image isn't going to give you the same data back. — Orion Lawlor, Oct 31 '19 at 23:25
@OrionLawlor thank you. in that case, after saving the image, how would i render it? — Alex Gordon, Oct 31 '19 at 23:30
Are you trying to render it as a response from the function, like via context.res? — search-learn, Aug 10 '20 at 00:49

search-learn · Accepted Answer · 2021-03-11T06:09:03.017

Well since you confirmed you are looking for output with context.res here is my working sample.. note that there is a maximum response size, so you can't return every image/file the way I am returning the image here

const Jimp = require('jimp')

module.exports = async function (context, req)
{
    let response = {}

    try
    {
        let url = 'https://noahwriting.com/wp-content/uploads/2018/06/APPLE-300x286.jpg'

        //call function to download and resize image
        response = await resizeImage(url)

    }
    catch (err)
    {
        response.type = 'application/json'
        if (err.response == undefined)
        {
            context.log(err)
            response.status = 500
            response.data = err
        }
        else
        {
            response.data = err.response.data
            response.status = err.response.status
            context.log(response)
        }
    }

    //response
    context.res =
    {
        headers: { 'Content-Type': `${response.type}` },
        body: response.buf
    }
}

async function resizeImage(url)
{
    //read image to buffer
    let image = await Jimp.read(url)

    //resize image
    image.resize(300, Jimp.AUTO)

    //save to buffer
    let image_buf = await image.getBufferAsync(image.getMIME())

    //image.getMIME() returns something like `image/jpeg` which is a valid Content-Type for responses.
    return { 'buf': image_buf, 'type': image.getMIME() }
}

(Offtopic but I saw that you are using blob storage so..) if you plan on storing photos/files/anything in Azure Blob Storage and you want to retrieve them in some systematic way you will find out very fast that you can't query the storage and you have to deal with ugly XML. My work around to avoid this way to create a function that stores photos/files in Blob Storage but then saves the url path to the file along with the file name and any other attributes to a mongo storage. So then I can make super fast queries to retrieve an array of links, which point to the respective files.

how to embed an image in a JSON response

1 Answers1