How to Build an End-to-End OCR Pipeline with Baidu’s Unlimited-OCR for High-Resolution Images and Multi-Page PDF Parsing

Images and Multi-Page PDF Parsing">

In this tutorial, we build a complete workflow for running Baidu’s Unlimited-OCR model on document images and multi-page PDFs. We configure the GPU environment, install the required dependencies, load the 3B-parameter vision-language model with automatic selection of bfloat16 or float16, and generate structured sample documents for testing. We then evaluate both the tiled Gundam inference mode and the faster Base mode for single-page OCR before extending the pipeline to multi-page PDF parsing with PyMuPDF and infer_multi(). Throughout the workflow, we preserve long-context generation settings, repetition controls, and structured output handling to process dense layouts, tables, paragraphs, and cross-page content in a reproducible end-to-end pipeline.

We install the required libraries and prepare the Google Colab environment for Unlimited-OCR inference. We verify that a CUDA-enabled GPU is available and automatically choose bfloat16 or float16 based on hardware support. We then load the tokenizer and the 3B-parameter model from Hugging Face, switch them to evaluation mode, and move them to the GPU.

We create the required input and output directories and generate three realistic sample document pages with PIL. We add headings, paragraphs, tables, and footnotes to test the model on structured, layout-rich content. We also preview the first generated page with Matplotlib before sending it to the OCR pipeline.

We run single-image OCR using Gundam mode, which combines a global document view with tiled image crops. We enable crop_mode and use a smaller tile size to preserve fine text and improve recognition on dense document layouts. We also configure long-output generation and repetition controls to ensure the model produces stable, structured results.

We process the same document using Base mode with a single 1024-pixel image view. We turn off image cropping to reduce inference complexity and improve processing speed for clean, clearly printed pages. We retain the same output length and repetition-control settings to directly compare Base mode with Gundam mode.

We create a three-page PDF from the generated document images and rasterize each page of the PDF into a high-resolution PNG using PyMuPDF. We pass the resulting page-image sequence to infer_multi() so that the model can parse the complete document in a single long-horizon inference operation. We also widen the n-gram repetition window to maintain stable decoding across multiple pages.

We inspect the output directories created by the single-page and multi-page inference runs. We list every generated file and display previews of supported text, Markdown, MMD, and JSON artifacts. We conclude the workflow with a concise reference summarizing the recommended inference modes for dense images, clean pages, and multi-page PDFs.