有没有办法以交互方式 select 感兴趣区域 (ROI)，然后在 python 上返回其 position

Question

I have a CT image array where I want to be able to select the region of interest on the plot itself and then return the position of the bounding-box rectangle/square, basically the start and the end of the rectangle/ square. Then I will crop the data py position: clipw = newdata[:,y1:y2,x1:x2].

I tried to use dash app and as shown here: https://dash.plotly.com/annotations it returns the charactaristics of the shapes by the callback functions which is useful but I have to copy and paste the positions myself. I cannot find a way to make it automatically pass the poition list to the next step (clipw). I am using Jupyter notebook.

Answer 1

If you intend to run your Dash app inside a Jupyter notebook, you'll probably want to use JupyterDash . To select the coordinates from the region of interest, there's an example further down on documentation page you linked that shows all of the information about the drawn shape including coordinates.

Below is an example of a JupyterDash app that can be run entirely inside your Jupyter notebook, and it selects the closest indices of your image by rounding the floating point x,y coordinates to integers. This relies on the fact that the shape of the image is (900,1600,3) and that plotly will be default set the x- and y-axes at the same scale.

Currently the app doesn't have much functionality except returning the closest x,y indices for the corners of your selected rectangle, but hopefully you can modify the rest of the function to fit your cropping use case.

import plotly.express as px
from jupyter_dash import JupyterDash
from dash import Dash, dcc, html, Input, Output, no_update
from skimage import io 
import json

img = io.imread('https://raw.githubusercontent.com/michaelbabyn/plot_data/master/bridge.jpg')
fig = px.imshow(img)
fig.update_layout(dragmode="drawrect")

app = JupyterDash(__name__)
app.layout = html.Div(
    [
        html.H3("Drag and draw rectangle annotations"),
        dcc.Graph(id="graph-picture", figure=fig),
        dcc.Markdown("Characteristics of shapes"),
        html.Pre(id="annotations-data"),
    ]
)

@app.callback(
    Output("annotations-data", "children"),
    Input("graph-picture", "relayoutData"),
    prevent_initial_call=True,
)
def on_new_annotation(relayout_data):
    if "shapes" in relayout_data:
        shape_dict = relayout_data["shapes"][0]
        x0, x1, y0, y1 = shape_dict["x0"], shape_dict["x1"], shape_dict["y0"], shape_dict["y1"]
        [x0, x1, y0, y1] = [round(num) for num in [x0, x1, y0, y1]]
        ## crop data
        return f"x0={x0}, x1={x1}, y0={y0}, y0={y1}"
    else:
        return no_update

app.run_server(mode='inline')