Version Compatibility

Reference examples tested with: matplotlib 3.8+, numpy 1.26+, pandas 2.2+, scikit-learn 1.4+

Before using code patterns, verify installed versions match. If versions differ:

• Python: pip show <package> then help(module.function) to check signatures

If code throws ImportError, AttributeError, or TypeError, introspect the installed package and adapt the example to match the actual API rather than retrying.

Interactive Annotation

"Manually annotate cell types in my IMC data" → Interactively label cells using napari visualization with marker overlays for training classifiers or validating automated phenotyping results.

• Python: napari.Viewer() with label layer for interactive annotation

Napari-Based Annotation

import napari
import numpy as np
from skimage import io
import pandas as pd

# Load IMC image stack
image_stack = io.imread('imc_image.tiff')  # (C, H, W)
segmentation_mask = io.imread('cell_segmentation.tiff')

# Create napari viewer
viewer = napari.Viewer()

# Add channels as separate layers for visualization
channel_names = ['CD45', 'CD3', 'CD68', 'panCK', 'DNA']
for i, name in enumerate(channel_names):
    viewer.add_image(image_stack[i], name=name, visible=False, colormap='gray', blending='additive')

# Add segmentation
viewer.add_labels(segmentation_mask, name='Cells')

# Add annotation layer (start empty)
annotation_layer = viewer.add_labels(
    np.zeros_like(segmentation_mask),
    name='Cell_Types'
)

# Define cell types
cell_type_mapping = {1: 'T_cell', 2: 'Macrophage', 3: 'Epithelial', 4: 'Stromal', 5: 'Other'}

Marker-Guided Annotation

def create_marker_overlay(image_stack, channel_indices, colors):
    '''Create RGB overlay of selected markers for easier annotation.'''
    h, w = image_stack.shape[1:]
    overlay = np.zeros((h, w, 3), dtype=np.float32)

    for idx, color in zip(channel_indices, colors):
        channel = image_stack[idx].astype(np.float32)
        channel = (channel - channel.min()) / (channel.max() - channel.min() + 1e-8)
        for c, weight in enumerate(color):
            overlay[:, :, c] += channel * weight

    overlay = np.clip(overlay, 0, 1)
    return overlay

# Create T cell overlay (CD3=green, CD45=blue)
t_cell_overlay = create_marker_overlay(
    image_stack,
    channel_indices=[0, 1],  # CD45, CD3
    colors=[[0, 0, 1], [0, 1, 0]]  # Blue, Green
)

# Create tumor overlay (panCK=red)
tumor_overlay = create_marker_overlay(
    image_stack,
    channel_indices=[3],  # panCK
    colors=[[1, 0, 0]]  # Red
)

# Add overlays to viewer
viewer.add_image(t_cell_overlay, name='T_cell_markers', visible=True)
viewer.add_image(tumor_overlay, name='Tumor_markers', visible=False)

Training Data Generation

def extract_training_data(image_stack, segmentation_mask, annotation_mask, channel_names):
    '''Extract mean marker intensities per cell with annotations.'''
    from skimage.measure import regionprops_table

    cells = []
    for cell_id in np.unique(segmentation_mask):
        if cell_id == 0:
            continue

        cell_mask = segmentation_mask == cell_id
        annotation = annotation_mask[cell_mask]
        annotation = annotation[annotation > 0]

        if len(annotation) == 0:
            continue

        cell_type = int(np.median(annotation))

        cell_data = {'cell_id': cell_id, 'cell_type': cell_type}
        for i, name in enumerate(channel_names):
            cell_data[name] = np.mean(image_stack[i][cell_mask])

        cells.append(cell_data)

    return pd.DataFrame(cells)

# After manual annotation in napari
annotation_data = annotation_layer.data
training_df = extract_training_data(image_stack, segmentation_mask, annotation_data, channel_names)
training_df.to_csv('training_annotations.csv', index=False)
print(f'Annotated {len(training_df)} cells')
print(training_df['cell_type'].value_counts())

Semi-Automated Annotation

Goal: Propagate a small set of manual cell type annotations to all unannotated cells using marker expression similarity.

Approach: Train a k-nearest-neighbors classifier on manually annotated cells' marker intensities, predict labels for remaining cells, and report classification confidence to flag uncertain assignments for review.

from sklearn.neighbors import KNeighborsClassifier
from sklearn.preprocessing import StandardScaler

def propagate_annotations(training_df, all_cells_df, marker_columns):
    '''Use annotated cells to classify unannotated cells.'''
    X_train = training_df[marker_columns].values
    y_train = training_df['cell_type'].values

    scaler = StandardScaler()
    X_train_scaled = scaler.fit_transform(X_train)

    knn = KNeighborsClassifier(n_neighbors=5)
    knn.fit(X_train_scaled, y_train)

    unannotated = all_cells_df[~all_cells_df['cell_id'].isin(training_df['cell_id'])]
    X_test = scaler.transform(unannotated[marker_columns].values)

    predictions = knn.predict(X_test)
    probabilities = knn.predict_proba(X_test)
    confidence = np.max(probabilities, axis=1)

    unannotated = unannotated.copy()
    unannotated['predicted_type'] = predictions
    unannotated['confidence'] = confidence

    return unannotated

marker_cols = ['CD45', 'CD3', 'CD68', 'panCK']
predictions = propagate_annotations(training_df, all_cells_df, marker_cols)

high_conf = predictions[predictions['confidence'] > 0.8]
print(f'{len(high_conf)} cells classified with high confidence')

Annotation Validation

def validate_annotations(annotation_df, image_stack, segmentation_mask, channel_names, output_dir):
    '''Generate validation plots for manual review.'''
    import matplotlib.pyplot as plt
    from pathlib import Path

    Path(output_dir).mkdir(exist_ok=True)

    cell_types = annotation_df['cell_type'].unique()

    for ct in cell_types:
        cells = annotation_df[annotation_df['cell_type'] == ct]
        n_sample = min(20, len(cells))
        sample_cells = cells.sample(n_sample)

        fig, axes = plt.subplots(n_sample, len(channel_names), figsize=(2*len(channel_names), 2*n_sample))

        for i, (_, cell) in enumerate(sample_cells.iterrows()):
            cell_mask = segmentation_mask == cell['cell_id']
            bbox = get_bounding_box(cell_mask, padding=10)

            for j, ch_name in enumerate(channel_names):
                ax = axes[i, j] if n_sample > 1 else axes[j]
                crop = image_stack[j][bbox[0]:bbox[1], bbox[2]:bbox[3]]
                ax.imshow(crop, cmap='gray')
                ax.axis('off')
                if i == 0:
                    ax.set_title(ch_name)

        plt.suptitle(f'Cell Type: {ct} (n={len(cells)})')
        plt.tight_layout()
        plt.savefig(f'{output_dir}/validation_type_{ct}.png', dpi=150)
        plt.close()

def get_bounding_box(mask, padding=10):
    rows = np.any(mask, axis=1)
    cols = np.any(mask, axis=0)
    rmin, rmax = np.where(rows)[0][[0, -1]]
    cmin, cmax = np.where(cols)[0][[0, -1]]
    rmin = max(0, rmin - padding)
    cmin = max(0, cmin - padding)
    rmax = min(mask.shape[0], rmax + padding)
    cmax = min(mask.shape[1], cmax + padding)
    return rmin, rmax, cmin, cmax

validate_annotations(training_df, image_stack, segmentation_mask, channel_names, 'validation/')

Napari Plugin Interface

from magicgui import magicgui
from napari.types import LabelsData

@magicgui(call_button='Apply Annotation')
def annotate_selected(viewer: napari.Viewer, cell_type: int = 1):
    '''Annotate selected cells with specified type.'''
    labels_layer = viewer.layers['Cells']
    annotation_layer = viewer.layers['Cell_Types']

    selected = labels_layer.selected_label
    if selected > 0:
        mask = labels_layer.data == selected
        annotation_layer.data[mask] = cell_type
        annotation_layer.refresh()
        print(f'Annotated cell {selected} as type {cell_type}')

@magicgui(call_button='Export Annotations')
def export_annotations(viewer: napari.Viewer, filename: str = 'annotations.csv'):
    '''Export current annotations to CSV.'''
    annotation_layer = viewer.layers['Cell_Types']
    segmentation_layer = viewer.layers['Cells']

    annotations = []
    for cell_id in np.unique(segmentation_layer.data):
        if cell_id == 0:
            continue
        cell_mask = segmentation_layer.data == cell_id
        cell_type = annotation_layer.data[cell_mask]
        cell_type = cell_type[cell_type > 0]
        if len(cell_type) > 0:
            annotations.append({'cell_id': cell_id, 'cell_type': int(np.median(cell_type))})

    pd.DataFrame(annotations).to_csv(filename, index=False)
    print(f'Exported {len(annotations)} annotations to {filename}')

# Add widgets to viewer
viewer.window.add_dock_widget(annotate_selected)
viewer.window.add_dock_widget(export_annotations)

Batch Annotation Workflow

def batch_annotation_session(image_files, seg_files, existing_annotations=None):
    '''Set up batch annotation session for multiple images.'''
    viewer = napari.Viewer()

    all_annotations = existing_annotations or {}

    for img_file, seg_file in zip(image_files, seg_files):
        image_stack = io.imread(img_file)
        seg_mask = io.imread(seg_file)

        sample_name = Path(img_file).stem

        for layer in list(viewer.layers):
            viewer.layers.remove(layer)

        for i, name in enumerate(channel_names):
            viewer.add_image(image_stack[i], name=name, visible=False)

        viewer.add_labels(seg_mask, name='Cells')

        if sample_name in all_annotations:
            viewer.add_labels(all_annotations[sample_name], name='Cell_Types')
        else:
            viewer.add_labels(np.zeros_like(seg_mask), name='Cell_Types')

        viewer.title = f'Annotating: {sample_name}'
        input('Press Enter when done annotating this image...')

        all_annotations[sample_name] = viewer.layers['Cell_Types'].data.copy()

    return all_annotations

Related Skills

• cell-segmentation - Generate cell masks for annotation
• phenotyping - Automated phenotyping as alternative
• spatial-analysis - Use annotations for spatial analysis
• quality-metrics - QC annotated data