How to Build a Simple OpenAI Image Generator with n8n

Opening Problem Statement

Imagine you’re Sarah, a graphic designer managing multiple clients who frequently request quick, unique visuals to complement their social media content. Manually creating each image is time-consuming, often taking up to an hour per piece, causing delays and reducing your ability to handle more projects.

Sarah needs a faster, automated solution to generate client-specific images on demand without deep technical expertise. She wants to offer custom-generated visuals instantly, saving hours each week and focusing on creative strategy rather than manual design tasks.

What This Automation Does

This Simple OpenAI Image Generator workflow built with n8n transforms text prompts into stunning images automatically. Here’s what happens when you run this workflow:

• Accepts image description and size from a user-submitted form.
• Uses OpenAI’s image generation model “GPT-Image-1” to create a unique image based on the prompt.
• Converts the OpenAI response from base64 encoded JSON to a downloadable image file format.
• Returns the generated image directly to the user through the form interface for easy download.
• Eliminates manual image creation steps, running end-to-end within a single automated flow.
• Saves significant time—potentially reducing hours of graphic design work to seconds per image.

Prerequisites 

Below are the exact tools and accounts needed to build and run this workflow:

• n8n account to create and manage the workflow.
• OpenAI API credentials for authenticating and accessing OpenAI’s image models. 🔑
• The built-in Form Trigger node in n8n to gather user inputs via a web form. 💬

If you prefer, you can self-host n8n for more control: check out this guide. ⚙️

Step-by-Step Guide to Build This Image Generator ⚙️

Step 1: Create your new workflow in n8n
Log in to your n8n dashboard, go to “Workflows” on the sidebar, and click on the “New Workflow” button. You should see a blank canvas ready for your nodes.

Common mistake: Forgetting to save your workflow early can lead to loss of progress.

Step 2: Add the Form Trigger node
Drag the Form Trigger node onto the canvas. Set the form title to “OpenAI Image Generator”. Add two fields: a required text field labeled “Prompt” (e.g., “Snow-covered mountain village in the Alps”) and a required dropdown for “Image size” with options: “1024×1024”, “1024×1536”, and “1536×1024”.

You should see the webhook URL generated in this node, which you can use to submit your form data.

Common mistake: Not marking fields as required will lead to incomplete inputs triggering errors downstream.

Step 3: Add the OpenAI Image Generation node (HTTP Request)
Add an HTTP Request node (configured for OpenAI API) after the Form Trigger. Set the method to POST and the URL to “https://api.openai.com/v1/images/generations”. In the body parameters, add:

{
  model: "gpt-image-1",
  prompt: "={{ $json.Prompt }}",
  n: 1,
  size: "={{ $json['Image size'] }}"
}

Use your OpenAI API credentials here for authentication.

You should see the API respond with image data encoded in base64 format.

Common mistake: Incorrect API keys or missing authentication cause request failures.

Step 4: Convert base64 response to a File
Add the Convert to File node next, selecting the operation “toBinary” and specifying the source property as “data[0].b64_json”. This transforms the encoded image data into a binary file n8n can handle.

You should see the image ready in file format to send back to the user.

Common mistake: Using the wrong source property results in empty or invalid files.

Step 5: Return the image to the form
Finally, add the Form node set to “completion” operation. Configure it to respond with a binary file using the output from the Convert to File node. Set the title to “Result” and the message to “Here is the created image:”.

You should be able to submit your form input via the webhook URL and get back a downloadable image instantly.

Common mistake: Forgetting to link the binary property correctly causes no file to be returned.

Customizations 

• Change image model: In the HTTP Request node, modify the “model” parameter value to experiment with other OpenAI image generation models if available. This changes the style and capabilities of the generated image.
• Add multiple image outputs: Increase the “n” value in the HTTP Request node from 1 to a higher number to generate more images per prompt, useful for client options.
• Customize form fields: In the Form Trigger node, add more fields such as “Style” or “Color palette” to give the user more control over image generation inputs.
• Save images to cloud storage: Add a cloud storage node (Google Drive, AWS S3) after Convert to File to automatically save generated images for future use.
• Add image watermark: Insert an additional node or external service call before returning the image to overlay branding or copyright marks.

Troubleshooting 

Problem: API request fails with “401 Unauthorized” error
Cause: Invalid or missing OpenAI credentials.
Solution: Go to the credentials section in n8n, re-enter your OpenAI API key, and make sure it’s assigned correctly to the HTTP Request node.

Problem: No image returned in the form response
Cause: Binary data not correctly linked.
Solution: Check the “Convert to File” node’s output property and ensure the Form node uses that binary property for the response.

Pre-Production Checklist 

• Confirm OpenAI API credentials are valid and have image generation enabled.
• Test form inputs with typical prompts and image sizes.
• Verify the binary file conversion step outputs a valid image file.
• Check form node response returns a downloadable image correctly in different browsers.
• Back up workflow JSON before making major changes.

Deployment Guide

Once you’ve tested and confirmed the workflow operates as expected, activate it in n8n by toggling the “Active” switch at the top right.

Share the webhook URL from the Form Trigger node with your users for image submissions.

Monitor the execution history in n8n to catch any errors or performance issues.

FAQs

Q: Can I use other image generation models besides “gpt-image-1”?
A: Yes, if OpenAI releases new models, you can update the model parameter in the HTTP Request node accordingly.

Q: Does this workflow consume OpenAI API credits?
A: Yes, each image generation request counts against your OpenAI API usage limits and may incur costs depending on your plan.

Q: Is my data secure in this workflow?
A: n8n keeps your data within your instance, and API calls authenticate through your own OpenAI credentials, ensuring control over data security.

Q: Can this scale to multiple simultaneous requests?
A: Yes, n8n can handle parallel executions, but plan your OpenAI usage to avoid rate limits.

Conclusion

By building this Simple OpenAI Image Generator with n8n, you now have a powerful, automated solution to transform text prompts into custom images instantly.

This saves hours of manual image creation, enhances your creative output, and offers a seamless experience for end-users or clients.

Next, consider automating image archiving, integrating with social media platforms for instant posting, or adding advanced controls for style and color directly in the input form.

Take pride in your automation skills and keep iterating for even greater efficiency. Happy automating!