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Gemini bounding boxes drawn on an image from a prompt

by Mindketn8n workflowDeveloper
Newversion 1 · updated
Nodes7Apps1Like

Overview

  1. When clicking ‘Test workflow’
  2. Get Test Image
  3. Get Image Info
  4. Gemini Object Detection
  5. Get Variables
  6. Scale Normalised Coords
  7. Draw Bounding Boxes
Gemini bounding boxes drawn on an image from a prompt, picture 1
‹2 / 2›

An n8n workflow that sends a picture and a short prompt to Google Gemini, then draws the boxes it returns on the picture. The prompt names what to find, and the sample asks for rabbits.

Gemini bounding boxes drawn on an image from a prompt is an n8n workflow in the Developer category, listed by Mindket. It is free. This is version 1, last updated on . Download it on this page or copy its JSON, then import it into an n8n canvas. Nothing runs until you activate it in n8n.

At a glance

Runs in
  • n8n Cloud: import the file there and run it by hand
  • Your own n8n server: the same file and steps
  • Google Gemini: the model that finds the matches
  • Your picture: a JPEG reachable by a web address

Platform

n8nWorkflow automation, in n8n’s cloud or on your own server
Connects 1 app

How it works

Trigger

Manual run

It starts when you click Test workflow in n8n:

  • The picture’s address, set in Get Test Image
  • The prompt, set in Gemini Object Detection

Actions

  1. The picture is downloaded and its width and height are read
  2. The picture and the prompt are sent to Gemini, which returns a box and a label for each match
  3. The boxes are scaled from a 0 to 1000 range to pixel positions and padded to six
  4. Six rectangles are drawn on the picture

Result

The picture with a box drawn around each match, up to six

Integrations

What you need before you start.

Google Gemini

Vision model

Looks at the picture, finds what the prompt names and returns a box and a label for each match.

NeedsA Google Gemini API key, saved in a Google Gemini(PaLM) API credential

Workflow check

Checked by Mindket on 13 Nov 2026

Steps
7 steps, starting by hand
AI
No step calls an AI model
Sign-ins
Signs in to: Google Gemini
API keys
No API key is left in the file
Step types
Mindket’s checker reads 4 of its 5 step types. It does not read: Edit Image

Read from the workflow’s file, not from a run.

About

What it is

This n8n workflow finds things in a picture from a plain sentence. It downloads an image and sends it to Google Gemini with a prompt that names what to find, here rabbits. Gemini answers with a box around each match. A Code node turns the boxes into pixel positions, and an Edit Image node draws them on the picture. Seven nodes run it, beside five sticky notes.

Who it suits

Builders who want to try prompt based object detection without training a model. Skip it if you need more than six boxes on a picture, exact outlines instead of rectangles, or a service that runs offline.

Who uses it, and how
IndustryWho uses itHow they use itExample
SoftwareDevelopersTest what Gemini finds in their own imagesA developer changes the prompt to cars and sees a box on each car in a street photo.
E-commerceCatalogue teamsMark the items in a product photoA team asks for shoes and checks that each pair gets a box.
ResearchAnalystsCheck how well a prompt finds a subjectAn analyst compares the boxes for two wordings of one prompt.
EducationTeachersShow how a vision model reads a pictureA teacher draws boxes on animals in a classroom photo.

You need some n8n: import a file, add one credential and paste the address of one picture.

Where to use it

Any n8n that can reach Google’s API and the address of your picture will run it. The result is a picture you open in the Draw Bounding Boxes node.

  • n8n Cloud: import the file there and run it by hand
  • Your own n8n server: the same file and steps
  • Google Gemini: the model that finds the matches
  • Your picture: a JPEG reachable by a web address

Setup

Download saves a zip with workflow.json and Mindket’s setup notes in your downloads folder. Setup takes one credential and one picture address.

What you need first
NeedDetail
n8nOn n8n Cloud or on a server of your own
Google GeminiAn API key, saved in a Google Gemini(PaLM) API credential
A pictureA JPEG file reachable by a web address
  1. In n8n, create a workflow, open its menu, choose Import from File and pick workflow.json.
  2. Add that credential with your key and select it in Gemini Object Detection.
  3. In Get Test Image, replace https://YOUR_IMAGE_HOST/your-image.jpg with your picture’s address.
  4. Change the prompt in the JSON body of Gemini Object Detection if you want to find something other than rabbits.
  5. Click Test workflow and open Draw Bounding Boxes to see the picture.

How to use it

Click Test workflow. After a few seconds the last node holds your picture with the boxes drawn on it. Change the prompt, and run it again to look for something else.

What to change for a different result
To changeWhere
What to findThe prompt in Gemini Object Detection
The pictureThe address in Get Test Image
The modelThe model name in the address of Gemini Object Detection
The look of a boxThe colour in each draw step of Draw Bounding Boxes

Example

A teacher saves a classroom photo of rabbits at a web address and pastes it into Get Test Image. She clicks Test workflow.

Gemini returns a box and a label for each rabbit it sees. The Code node scales the boxes to the photo’s size, and the last node shows the photo with a box on each rabbit.

For newcomers and experts

If you are new. n8n draws a workflow as boxes joined by lines, and each box, a node, does one job. Here one node asks Gemini, one does the sums and one draws. Start with a clear picture that has two or three subjects.

For experts. Gemini is called through an HTTP Request node with a response schema that asks for a list of objects with a box_2d and a label. There is no Gemini node and no AI Agent.

Where to look closer
NodeWhat it doesWhat to know
Gemini Object DetectionPosts the picture and the prompt to the generateContent endpointThe picture goes in as base64 in the JSON body
Get VariablesReads the model’s text as JSONIt uses parseJson, so a reply that is not JSON stops the run
Scale Normalised CoordsTurns the 0 to 1000 boxes into pixels and pads them to sixThe extra boxes beyond six are cut
Draw Bounding BoxesDraws six rectangles on the pictureAn empty slot becomes a zero size box at the top left corner

Good to know

Only six boxes are drawn, and the model name was changed because the original one is not on Google’s current pages.

  • The repair: Google’s deprecations page, read on 12 November 2026, does not list the original gemini-2.0-flash-exp, shows the gemini-2.0-flash family shut down on 1 June 2026 and names gemini-3.6-flash as the replacement. This copy uses that
  • The fix for few matches: the original failed on a picture with fewer than six matches. The Code node now pads the list
  • Box format: Google’s image guide, read on 12 November 2026, gives each box as [ymin, xmin, ymax, xmax] on a scale of 0 to 1000
  • Output: the picture stays inside n8n, so add a node to save or send it
  • The format: the request marks the picture as JPEG, so other formats need a change in the body
  • Large pictures: the request carries the whole picture as text, so a big one makes a big request
  • Your data: the picture and the prompt go to Google
  • Credentials: the JSON holds none

README and files

README

Gemini bounding boxes drawn on an image from a prompt

An n8n workflow that sends one picture and a short prompt to Google's Gemini. Gemini answers with a box around each match,
and the workflow draws those boxes on the picture. The prompt asks for rabbits, and you can change it to ask for anything
you can name.

What is inside

  • workflow.json: the workflow as n8n exports it, twelve nodes: seven that do the work and five sticky notes. It holds no
    credential.
  • README.md: these notes.

What we changed from the original copy

  • The model was gemini-2.0-flash-exp. Google's deprecations page, read on 12 November 2026, does not list that name, but
    it shows the gemini-2.0-flash family shut down on 1 June 2026 and names gemini-3.6-flash as the replacement. The
    request now goes to gemini-3.6-flash.
  • The node that asks Gemini was called Gemini 2.0 Object Detection. It is now Gemini Object Detection, since the model
    changed.
  • Get Test Image downloaded a picture from the author's own address. It now holds https://YOUR_IMAGE_HOST/your-image.jpg.
  • Draw Bounding Boxes has six fixed draw steps and read a box from each. A picture with fewer than six matches made the
    workflow fail on a missing box. The Code node now pads the list to six, and extra boxes beyond six are cut.
  • The sticky notes are rewritten as short notes about each step, without their links. Two are gone: one held a picture of
    the author's own output and one explained why a different node was not used.
  • Nothing else.

Before you start

  • An n8n instance, on n8n Cloud or your own server.
  • A Google Gemini API key, in a Google Gemini(PaLM) API credential.
  • A picture that Gemini accepts, reachable by a web address. The workflow sends it as JPEG, so use a JPEG file.

Set it up

  1. In n8n, create a workflow, open its menu and choose Import from File. Pick workflow.json.
  2. Add that credential with your key and select it in Gemini Object Detection.
  3. In Get Test Image, replace https://YOUR_IMAGE_HOST/your-image.jpg with the address of your picture.
  4. In Gemini Object Detection, change the prompt in the JSON body if you want something other than rabbits.
  5. Click Test workflow and open Draw Bounding Boxes to see the picture.

How a run goes

  1. Get Test Image downloads the picture, and Get Image Info reads its width and height.
  2. Gemini Object Detection posts the picture and the prompt, and asks for a JSON list in which each match has a box_2d
    list and a label.
  3. Get Variables reads the model's text as JSON, and keeps the picture's width and height next to it.
  4. Scale Normalised Coords turns each box into pixel positions and pads the list to six boxes.
  5. Draw Bounding Boxes draws the six boxes on the picture it holds.

Change the look

  • What to find: the words of the prompt in Gemini Object Detection.
  • The picture: the address in Get Test Image.
  • The model: the model name in the address of Gemini Object Detection.
  • The colour of the boxes: the colour field of each draw step in Draw Bounding Boxes.

Good to know

  • Google's image guide, read on 12 November 2026, gives each box as [ymin, xmin, ymax, xmax] on a scale of 0 to 1000. The
    Code node turns that into pixels with the picture's width and height.
  • Only six boxes are drawn. A seventh match is dropped. For more, add draw steps and extend the padding in the Code node.
  • An empty slot becomes a box of zero size at the top left corner, which shows as a dot or nothing. It is not a match.
  • Get Variables reads the model's text with parseJson. If the model answers with something that is not JSON, the run
    stops there.
  • The Code node reads the binary picture from Get Test Image, so a change to that node's name needs the same change in the
    Code node.
  • The request sends the picture as base64 inside the JSON body, so a large picture makes a large request.
  • Google's deprecations page also routes gemini-2.5-pro and gemini-2.5-flash to newer models from 1 December 2026, so
    check the page again before you pick another model.
  • The picture goes to Google.
  • The JSON holds no credential.
Files
NOTICE.md  618 B
README.md  4 KB
workflow.json  11 KB

3 files, 15 KB, downloaded as a zip.

What’s new

  • Version 1 · 2026-11-12

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