chore: import upstream snapshot with attribution

2026-07-13 13:05:14 +08:00
commit 2a547be7fe
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+<!--[metadata]
+title = "Live camera edge detection"
+tags = ["2D", "Canny", "Live", "OpenCV"]
+thumbnail = "https://static.rerun.io/live-camera-edge-detection/f747bcf9ff3039c895f0bf0290e2dea0a72631ea/480w.png"
+thumbnail_dimensions = [480, 480]
+-->
+
+Visualize the [OpenCV Canny Edge Detection](https://docs.opencv.org/4.x/da/d22/tutorial_py_canny.html) results from a live camera stream.
+
+<picture>
+  <source media="(max-width: 480px)" srcset="https://static.rerun.io/live_camera_edge_detection/bf877bffd225f6c62cae3b87eecbc8e247abb202/480w.png">
+  <source media="(max-width: 768px)" srcset="https://static.rerun.io/live_camera_edge_detection/bf877bffd225f6c62cae3b87eecbc8e247abb202/768w.png">
+  <source media="(max-width: 1024px)" srcset="https://static.rerun.io/live_camera_edge_detection/bf877bffd225f6c62cae3b87eecbc8e247abb202/1024w.png">
+  <source media="(max-width: 1200px)" srcset="https://static.rerun.io/live_camera_edge_detection/bf877bffd225f6c62cae3b87eecbc8e247abb202/1200w.png">
+  <img src="https://static.rerun.io/live_camera_edge_detection/bf877bffd225f6c62cae3b87eecbc8e247abb202/full.png" alt="Live Camera Edge Detection example screenshot">
+</picture>
+
+## Used Rerun types
+[`Image`](https://www.rerun.io/docs/reference/types/archetypes/image)
+
+## Background
+In this example, the results of the [OpenCV Canny Edge Detection](https://docs.opencv.org/4.x/da/d22/tutorial_py_canny.html) algorithm are visualized.
+Canny Edge Detection is a popular edge detection algorithm, and can efficiently extract important structural information from visual objects while notably reducing the computational load.
+The process in this example involves converting the input image to RGB, then to grayscale, and finally applying the Canny Edge Detector for precise edge detection.
+
+## Logging and visualizing with Rerun
+
+The visualization in this example were created with the following Rerun code:
+### RGB image
+
+The original image is read and logged in RGB format under the entity "image/rgb".
+```python
+# Log the original image
+rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
+rr.log("image/rgb", rr.Image(rgb))
+```
+
+### Grayscale image
+
+The input image is converted from BGR color space to grayscale, and the resulting grayscale image is logged under the entity "image/gray".
+```python
+# Convert to grayscale
+gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
+rr.log("image/gray", rr.Image(gray))
+```
+
+### Canny edge detection image
+
+The Canny edge detector is applied to the grayscale image, and the resulting edge-detected image is logged under the entity "image/canny".
+```python
+# Run the canny edge detector
+canny = cv2.Canny(gray, 50, 200)
+rr.log("image/canny", rr.Image(canny))
+```
+
+
+## Run the code
+To run this example, make sure you have the Rerun repository checked out and the latest SDK installed:
+```bash
+pip install --upgrade rerun-sdk  # install the latest Rerun SDK
+git clone git@github.com:rerun-io/rerun.git  # Clone the repository
+cd rerun
+git checkout latest  # Check out the commit matching the latest SDK release
+```
+Install the necessary libraries specified in the requirements file:
+```bash
+pip install -e examples/python/live_camera_edge_detection
+```
+To experiment with the provided example, simply execute the main Python script:
+```bash
+python -m live_camera_edge_detection # run the example
+```
+If you wish to customize it, explore additional features, or save it use the CLI with the `--help` option for guidance:
+```bash
+python -m live_camera_edge_detection --help
+```
@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+"""
+Very simple example of capturing from a live camera.
+
+Runs the opencv canny edge detector on the image stream.
+"""
+
+from __future__ import annotations
+
+import argparse
+
+import cv2
+
+import rerun as rr  # pip install rerun-sdk
+import rerun.blueprint as rrb
+
+
+def run_canny(num_frames: int | None) -> None:
+    # Create a new video capture
+    cap = cv2.VideoCapture(0)
+
+    frame_nr = 0
+
+    while cap.isOpened():
+        if num_frames and frame_nr >= num_frames:
+            break
+
+        # Read the frame
+        ret, img = cap.read()
+        if not ret:
+            if frame_nr == 0:
+                print("Failed to capture any frame. No camera connected?")
+            else:
+                print("Can't receive frame (stream end?). Exiting…")
+            break
+
+        # Get the current frame time. On some platforms it always returns zero.
+        frame_time_ms = cap.get(cv2.CAP_PROP_POS_MSEC)
+        if frame_time_ms != 0:
+            rr.set_time("frame_time", duration=1e-3 * frame_time_ms)
+
+        rr.set_time("frame_nr", sequence=frame_nr)
+        frame_nr += 1
+
+        # Log the original image
+        rr.log("image/rgb", rr.Image(img, color_model="BGR"))
+
+        # Convert to grayscale
+        gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
+        rr.log("image/gray", rr.Image(gray))
+
+        # Run the canny edge detector
+        canny = cv2.Canny(gray, 50, 200)
+        rr.log("image/canny", rr.Image(canny))
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="Streams a local system camera and runs the canny edge detector.")
+    parser.add_argument(
+        "--device",
+        type=int,
+        default=0,
+        help="Which camera device to use. (Passed to `cv2.VideoCapture()`)",
+    )
+    parser.add_argument("--num-frames", type=int, default=None, help="The number of frames to log")
+
+    rr.script_add_args(parser)
+    args = parser.parse_args()
+
+    rr.script_setup(
+        args,
+        "rerun_example_live_camera_edge_detection",
+        default_blueprint=rrb.Vertical(
+            rrb.Horizontal(
+                rrb.Spatial2DView(origin="/image/rgb", name="Video"),
+                rrb.Spatial2DView(origin="/image/gray", name="Video (Grayscale)"),
+            ),
+            rrb.Spatial2DView(origin="/image/canny", name="Canny Edge Detector"),
+            row_shares=[1, 2],
+        ),
+    )
+
+    run_canny(args.num_frames)
+
+    rr.script_teardown(args)
+
+
+if __name__ == "__main__":
+    main()
@@ -0,0 +1,16 @@
+[project]
+name = "live_camera_edge_detection"
+version = "0.1.0"
+# requires-python = "<3.12"
+readme = "README.md"
+dependencies = ["opencv-python", "rerun-sdk"]
+
+[project.scripts]
+live_camera_edge_detection = "live_camera_edge_detection:main"
+
+[tool.rerun-example]
+extra-args = "--num-frames=30"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"