GenAI Image Alt Text

It is a best practice to provide an alt attribute for images.
This attribute is used to describe the image to users who are unable to see it.
It is also used by search engines to understand the content of the image.

<img src="..." alt="describe the image here" />

However, this task can be tedious and developer are often tempted to skip it, or provide a generic alt text like "image".

<img src="..." alt="image" />

GenAI to the rescue

To solve this issue, we created a GenAIScript script that uses the OpenAI Vision model (gpt-4-turbo-v or gpt-4o) to analyze the documentation images and generate a description alt text.

We assume that the script is run on a single image file
and we use defImages (provided by GenAIScript) to add it to the prompt context.

const file = env.files[0] // selected in UI or cli
defImages(file) // encode image in openai json payload

Then we give a task to the LLM to generate a good alt text.

$`You are an expert in assistive technology. 
Generate a description alt text for the image.`

finally, we use defFileOutput to define a file output route.

defFileOutput(file.filename + ".txt", `Alt text for image ${file.filename}`)

Usage in Astro

The GenAIScript documentation uses Astro, which allows to author pages in MDX.
The code below shows how the generate alt text, stored in a separate text file, is injected in the final HTML.

import { Image } from "astro:assets"
import src from "../../../assets/debugger.png"
import alt from "../../../assets/debugger.png.txt?raw"

<Image src={src} alt={alt} />

The debugger.png image shows the screenshot of a debugging session and the generate alt text file contents.

Full source

script({ model: "openai:gpt-4-turbo-v", maxTokens: 4000, })
const file = env.files[0]
defImages(file)
$`You are an expert in assistive technology. 
Generate a description alt text for the image.
- Do not include Alt text in the description.`
defFileOutput(file.filename + ".txt", `Alt text for image ${file.filename}`)