How to use multimodal prompts

Here we demonstrate how to use prompt templates to format multimodal inputs to models.

In this example we will ask a model to describe an image.

import base64

import httpx

image_url = "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Gfp-wisconsin-madison-the-nature-boardwalk.jpg/2560px-Gfp-wisconsin-madison-the-nature-boardwalk.jpg"
image_data = base64.b64encode(httpx.get(image_url).content).decode("utf-8")

from langchain_core.prompts import ChatPromptTemplate
from langchain_openai import ChatOpenAI

model = ChatOpenAI(model="gpt-4o")

API Reference:ChatPromptTemplate | ChatOpenAI

prompt = ChatPromptTemplate.from_messages(
    [
        ("system", "Describe the image provided"),
        (
            "user",
            [{"type": "image_url", "image_url": "data:image/jpeg;base64,{image_data}"}],
        ),
    ]
)

chain = prompt | model

response = chain.invoke({"image_data": image_data})
print(response.content)

The image depicts a sunny day with a beautiful blue sky filled with scattered white clouds. The sky has varying shades of blue, ranging from a deeper hue near the horizon to a lighter, almost pale blue higher up. The white clouds are fluffy and scattered across the expanse of the sky, creating a peaceful and serene atmosphere. The lighting and cloud patterns suggest pleasant weather conditions, likely during the daytime hours on a mild, sunny day in an outdoor natural setting.

We can also pass in multiple images.

prompt = ChatPromptTemplate.from_messages(
    [
        ("system", "compare the two pictures provided"),
        (
            "user",
            [
                {
                    "type": "image_url",
                    "image_url": "data:image/jpeg;base64,{image_data1}",
                },
                {
                    "type": "image_url",
                    "image_url": "data:image/jpeg;base64,{image_data2}",
                },
            ],
        ),
    ]
)

chain = prompt | model

response = chain.invoke({"image_data1": image_data, "image_data2": image_data})
print(response.content)

The two images provided are identical. Both images feature a wooden boardwalk path extending through a lush green field under a bright blue sky with some clouds. The perspective, colors, and elements in both images are exactly the same.