gigapath/preprocessing/data/slide_utils.py

import openslide

def find_level_for_target_mpp(slide_path, target_mpp):
    """
    Find the level in the slide that corresponds to the target MPP.

    Parameters:
    slide_path (str): Path to the slide file.
    target_mpp (float): Target microns per pixel (MPP).

    Returns:
    int: Level number that corresponds to the target MPP or None if not found.
    """
    slide = openslide.OpenSlide(slide_path)

    print(slide.properties)

    # Retrieve resolution information from properties
    x_resolution = float(slide.properties.get('tiff.XResolution'))
    y_resolution = float(slide.properties.get('tiff.YResolution'))
    resolution_unit = slide.properties.get('tiff.ResolutionUnit')

    # Convert resolution to microns per pixel (MPP)
    if resolution_unit == 'centimeter':
        mpp_x = 10000 / x_resolution
        mpp_y = 10000 / y_resolution
    else:
        print("Resolution unit is not in centimeters. Adjust the calculation accordingly.")
        return None

    # Check if MPP information is available
    if not mpp_x or not mpp_y:
        print("Could not calculate MPP due to missing or invalid resolution information.")
        return None

    # Iterate through each level and calculate MPP
    for level in range(slide.level_count):
        # Calculate MPP for the current level
        level_mpp_x = mpp_x * slide.level_downsamples[level]
        level_mpp_y = mpp_y * slide.level_downsamples[level]

        # Check if this level's MPP is close to the target MPP
        if abs(level_mpp_x - target_mpp) < 0.1 and abs(level_mpp_y - target_mpp) < 0.1:
            print(f"Level {level} corresponds to approximately {target_mpp} MPP.")
            return level

    print(f"No level corresponds to approximately {target_mpp} MPP.")
    return None