Mouse drag callback

Example updating the status bar with line profile info while dragging lines around in a shapes layer.

Tags: gui

import numpy as np
from skimage import data, measure

import napari


def profile_lines(image, shape_layer):
    profile_data = [
        measure.profile_line(image, line[0], line[1], mode='reflect').mean()
        for line in shape_layer.data
    ]
    print(f"profile means: [{', '.join(f'{d:.2f}' for d in profile_data)}]")


np.random.seed(1)
viewer = napari.Viewer()
blobs = data.binary_blobs(length=512, volume_fraction=0.1, n_dim=2)
viewer.add_image(blobs, name='blobs')
line1 = np.array([[11, 13], [111, 113]])
line2 = np.array([[200, 200], [400, 300]])
lines = [line1, line2]
shapes_layer = viewer.add_shapes(
    lines,
    shape_type='line',
    edge_width=5,
    edge_color='coral',
    face_color='royalblue',
)
shapes_layer.mode = 'select'


@shapes_layer.mouse_drag_callbacks.append
def profile_lines_drag(layer, event):
    profile_lines(blobs, layer)
    yield
    while event.type == 'mouse_move':
        profile_lines(blobs, layer)
        # the yield statement allows the mouse UI to keep working while
        # this loop is executed repeatedly
        yield


if __name__ == '__main__':
    napari.run()