How can I fix the 'invalid mime type' error when sending an image as a binary string to Stability AI in Express?

Question

I am trying to use the image-to-image API from stabilityAI. I need to send an image as binary string in my express server to the stability AI API, when I send the POST request to the API I get this error:

return
invalid mime type for init_image: application/octet-stream is not image/jpeg, image/png, image/gif, or image/webp.

The documentation says I need to send it as string binary I am sending the image from the frontend as a base 64 and receive it in this function.

app.post('/transform', async(req, res) => {
    const formData = new FormData();
    let data = req.body.image;
  // Convert Base64 to binary
    const imagePath = 'src/assets/images/image2.png';
    const imageBuffer = Buffer.from(data, 'base64');
    fs.writeFileSync(imagePath, imageBuffer);
    formData.append('init_image', imageBuffer, {filename: 'image.jpg',  contentType: 'image/png'})
    formData.append('init_image_mode', 'IMAGE_STRENGTH')
    formData.append('image_strength', '.40')
    formData.append('text_prompts[0][text]', 'Galactic dog wearing a cape')
    formData.append('text_prompts[0][weight]', '0.5'); // Sample weight
    formData.append('cfg_scale', '7')
    formData.append('clip_guidance_preset', 'FAST_BLUE')
    formData.append('samples', '1')
    formData.append('steps', '30')


   try {
    const response = await axios.post(url, formData, {
      headers: {
        'Content-Type': 'multipart/form-data',
        'Accept': 'application/json', // Update the Accept header
        'Authorization': `Bearer ${apiKey}`,
      },
    });

    const responseData = response.data;
    console.log(responseData);
    res.send(responseData);
  } catch (error) {
    console.error(error);
    res.sendStatus(500);
  }
})

I tried sending it as base 64 and converting it to binary but it doesn't seem to work. Any help would be appreciated.

Answer 1

What worked for me was to add const FormData = require('form-data'); at the top, whereas I didn't have anything before.

I don't exactly know why this fixed it, but I guess there are two different FormData modules kicking around, and the "built-in" one behaves differently in a way that the stability.ai API doesn't like.