Set Alternate Description BLIP is a free, local Docker action that generates alt text for Figure tags in a PDF. It uses Salesforce’s BLIP vision-language model, so it never sends your images to a cloud API. You can also run it on a single image file, not just a full PDF.
Key Capabilities
Runs locally, fits your workflow
Action Summary
| Free · Local | Set Alternate Description | Automatically generates alternate text for Figure tags using Salesforce BLIP large, embedding it into each figure’s Alt attribute |
| Free · Local | Set Alternate Description | Automatically generates alternate text from an image file using Salesforce BLIP large, saving the description to a text file |
Frequently Asked Questions
What is Salesforce BLIP?
BLIP – Bootstrapping Language-Image Pretraining – is an open-source vision-language model developed by Salesforce Research. It is trained to understand and describe image content in natural language. The PDFix action uses the BLIP-large variant, which offers higher description accuracy than the base model.
Does this action require an internet connection or API key?
No. The BLIP model runs entirely on your local machine inside a Docker container. No image data is transmitted to Salesforce, PDFix, or any third-party service. This makes it suitable for use with confidential or regulated documents.
How accurate are the generated descriptions?
BLIP-large produces accurate descriptions for photographs, diagrams, and general figures. For highly specialized technical images – such as engineering schematics, medical scans, or complex charts – the generated descriptions should be reviewed by a human before finalizing. PDFix Desktop allows you to edit any generated alt text before saving.
How does this differ from the Generate Alternate Text (OpenAI) action?
Both actions generate alt text for PDF images, but they differ in cost and data handling. The Salesforce BLIP action is 100% free and runs entirely on your local machine with no data leaving your environment. The OpenAI action connects to the OpenAI API, requires an API key, and is billed per use – but can produce more nuanced descriptions for complex or context-dependent images.
