Histolab

When to Use

• You need to tile gigapixel Whole Slide Images (WSI) into manageable patches for downstream analysis.
• You want automatic tissue detection to avoid background-heavy tiles during dataset preparation.
• You are building a simple, fast preprocessing pipeline (e.g., thresholding + morphology) for H&E slides.
• You need random sampling, grid coverage, or score-based selection of tiles for exploratory analysis or model training.
• You want to preview masks and tile locations before running extraction to validate parameters quickly.

Note: For advanced multiplex/spatial workflows or complex deep learning pipelines, consider more specialized frameworks (e.g., PathML).

Key Features

• Slide management via Slide: load WSI formats (SVS, TIFF, NDPI, etc.), access metadata, thumbnails, pyramid levels, and regions.
• Tissue masking via TissueMask, BiggestTissueBoxMask, and custom BinaryMask implementations.
• Tile extraction strategies:
  • RandomTiler (random sampling with reproducible seeds)
  • GridTiler (systematic coverage with optional overlap)
  • ScoreTiler (top-N tiles by a scoring function such as nuclei density)
• Preprocessing filters (image + morphology) and filter pipelines via Compose.
• Visualization helpers to preview masks (locate_mask) and tile locations (locate_tiles) and to review extracted tiles.

Reference docs (optional, for deeper detail):

• references/slide_management.md
• references/tissue_masks.md
• references/tile_extraction.md
• references/filters_preprocessing.md
• references/visualization.md

Dependencies

• histolab (install via pip/uv; version depends on your environment)

Installation:

uv pip install histolab

Example Usage

A complete, runnable example that loads a slide, builds a tissue mask, previews tile locations, and extracts tiles.

from pathlib import Path

from histolab.slide import Slide
from histolab.masks import TissueMask
from histolab.tiler import RandomTiler

def main():
    slide_path = "slide.svs"  # replace with your WSI path
    out_dir = Path("output")
    out_dir.mkdir(parents=True, exist_ok=True)

    # 1) Load slide
    slide = Slide(slide_path, processed_path=str(out_dir))

    # 2) Build/preview tissue mask
    tissue_mask = TissueMask()
    slide.locate_mask(tissue_mask)  # writes a visualization into processed_path

    # 3) Configure tiler
    tiler = RandomTiler(
        tile_size=(512, 512),
        n_tiles=100,
        level=0,
        seed=42,
        check_tissue=True,
        tissue_percent=80.0,
    )

    # 4) Preview tile locations (recommended before extraction)
    tiler.locate_tiles(slide, n_tiles=20)

    # 5) Extract tiles (restricted to tissue mask)
    tiler.extract(slide, extraction_mask=tissue_mask)

    print("Done. Check the output directory for thumbnails, mask previews, and tiles.")

if __name__ == "__main__":
    main()

Implementation Details

Slide and pyramid levels

• WSIs are typically stored as pyramids (multiple resolutions).
• level=0 usually means highest resolution (slowest, largest output).
• Using level=1 or level=2 can significantly improve throughput for dataset prototyping.

Tissue masking

• TissueMask generally segments all tissue regions (useful when multiple fragments exist).
• BiggestTissueBoxMask focuses on the largest tissue region (often faster and cleaner for single-section slides).
• Masks can be customized by passing a filter pipeline (see references/tissue_masks.md and references/filters_preprocessing.md).

Tile extraction strategies and key parameters

• Common parameters
  • tile_size=(w, h): output tile dimensions in pixels at the chosen pyramid level.
  • check_tissue=True: enables tissue-content filtering.
  • tissue_percent: minimum tissue coverage required for a tile to be accepted (commonly 70–90).
  • extraction_mask: restricts candidate tile locations to a mask-defined ROI.
• RandomTiler
  • n_tiles: number of tiles to sample.
  • seed: ensures reproducibility across runs.
• GridTiler
  • pixel_overlap: overlap between adjacent tiles (0 for non-overlapping grids).
• ScoreTiler
  • scorer: ranks tiles (e.g., NucleiScorer) and selects top tiles.
  • Often used with a CSV report (report_path) for auditability.

Filters and preprocessing pipelines

• Filters are typically chained using Compose to build repeatable pipelines (e.g., grayscale → threshold → morphology).
• These pipelines can be used to:
  • improve tissue segmentation robustness,
  • remove small artifacts/holes,
  • tailor detection to staining variability.

For concrete filter recipes and parameter guidance, see references/filters_preprocessing.md.