医学图像OrthoSlicer3D点击事件获取zdata报错：MouseEvent无zdata属性

Let's break down why you're running into this error and how to fix it properly. The core issue here is that MouseEvent objects don't have a built-in zdata attribute—that value (your slice index) is custom to your medical image viewing workflow, not something Matplotlib's event system provides out of the box.

Why This Happens #

When you try to grab event.zdata from a toolbar click event, you're assuming the event carries your 3D slice data directly. But Matplotlib's MouseEvent only contains info about the click itself (like position, button pressed, which axes it occurred on)—it doesn't track your custom slice state.

Solution: Track Slice State Manually #

The fix involves maintaining your own slice index variable, updating it when the navigation toolbar buttons are clicked, and using that variable as your "zdata". Here's a complete, working example:

import nibabel as nib
import matplotlib.pyplot as plt
from matplotlib.backend_bases import MouseButton
import numpy as np

# Load your NII file
nii_file_path = "your_medical_image.nii.gz"
nii_img = nib.load(nii_file_path)
image_data = nii_img.get_fdata()
# Get dimensions: assuming (x, y, z) where z is the slice axis
x_dim, y_dim, num_slices = image_data.shape

# Initialize current slice (start at the middle)
current_slice = num_slices // 2

# Set up the plot
fig, ax = plt.subplots()
# Display the initial slice
img_display = ax.imshow(image_data[:, :, current_slice], cmap="gray")
ax.set_title(f"Slice Index: {current_slice}")

# Helper function to update the displayed slice
def update_displayed_slice(new_slice_idx):
    global current_slice
    # Make sure we don't go out of bounds
    if 0 <= new_slice_idx < num_slices:
        current_slice = new_slice_idx
        img_display.set_data(image_data[:, :, current_slice])
        ax.set_title(f"Slice Index: {current_slice}")
        # Refresh the plot
        fig.canvas.draw_idle()

# Handle toolbar click events
def on_toolbar_click(event):
    # Only respond to left-clicks on toolbar buttons
    if event.button == MouseButton.LEFT:
        # Access the GUI button that was clicked (works for Qt backend; adjust if using others)
        clicked_button = event.guiEvent.sender()
        button_label = clicked_button.text()
        
        # Update slice based on which toolbar button was pressed
        if button_label == "Previous":
            update_displayed_slice(current_slice - 1)
        elif button_label == "Next":
            update_displayed_slice(current_slice + 1)
    
    # Now you can access the current slice (your "zdata") anywhere in this function
    print(f"Current zdata (slice index): {current_slice}")

# Bind the click event to the figure canvas
fig.canvas.mpl_connect('button_press_event', on_toolbar_click)

plt.show()

Key Notes: #

1. State Tracking: We use current_slice to keep track of the active slice index—this is your "zdata".
2. Toolbar Button Detection: We check the text of the clicked toolbar button to decide whether to increment or decrement the slice index. Note: Button labels might vary slightly across Matplotlib backends (e.g., Tkinter vs Qt), so adjust the text checks if needed.
3. Safe Updates: We add bounds checking to avoid trying to access slices that don't exist (e.g., slice -1 or slice num_slices).

Alternative: Grab Slice Data from the Displayed Image #

If you don't want to track a separate variable, you can also derive the current slice from the displayed image's data, but this only works if you're updating the image data directly (like we do in update_displayed_slice):

# Inside your click event handler
current_displayed_data = img_display.get_array()
# Find which slice in the original data matches this (might be slower for large datasets)
current_slice = np.where((image_data == current_displayed_data).all(axis=(0,1)))[0][0]

But tracking current_slice directly is more efficient and reliable.

内容的提问来源于stack exchange，提问作者user9535201