cristhian
dc3960809a
The build command was `pip install .`, which is what upstream and the dora docs use because `--uv` rewrites it. Spelling it `uv pip install .` means the dataflow never installs through pip at all, whether or not `--uv` was passed. The cost is that the node then needs a virtualenv to install into, so it must be run with `--uv`; the README says so. The second dataflow is gone. It existed to wire this node into dora-image-view just to see the frames, which pulled another repository over the network and needed a tag there. PREVIEW=true now opens a local window of the frames as they are published, so checking a camera, an encoding or a flip needs this repository alone. It shows the frame after the flip and the resize, so what is on screen is what is sent, and it never opens under CI, where there is no display. That a source node can display its own output overlaps with what a viewer node does. The overlap is the point: the alternative was a second repository in the loop before you can tell whether a camera works.
dora-webcam
Dora node that captures frames from a webcam and publishes them as
std/media/v1/Image. A source for a vision pipeline: it takes a tick and produces
frames.
Based on opencv-video-capture
from dora-hub, brought up to the dora 1.0 node contract, narrowed to Linux camera
selection, and changed to publish the typed Arrow image struct rather than a flat
buffer plus metadata.
Usage
Add to your dataflow:
nodes:
- id: camera
git: ssh://git@gitea.liria.cl:5001/liria/dora-webcam.git
tag: v0.1.0
build: uv pip install .
path: dora-webcam
inputs:
tick: dora/timer/millis/33
outputs:
- image
Run the dataflow with --uv (dora run dataflow.yml --uv): the build command is
uv pip install ., so the node gets its own managed environment and never installs into
an ambient one.
Runnable dataflow
dataflow.yml is the camera on its own, and is what CI runs:
dora run dataflow.yml --uv
Nothing consumes the frames, so to actually see them set PREVIEW:
PREVIEW=true dora run dataflow.yml --uv
A window opens showing the frames as they are published. Press q to stop. That is
enough to check a camera, an encoding or a flip without wiring a second node — which is
why there is one dataflow here rather than one per consumer.
For a real pipeline, wire image into a viewer such as dora-image-view from your own
dataflow.
Output
| Output | Payload | Metadata |
|---|---|---|
image |
std/media/v1/Image struct |
none — the struct describes itself |
The struct carries width: UInt32, height: UInt32, encoding: Utf8 and
data: LargeBinary, so a receiver needs nothing from the message metadata. For a
compressed encoding, width and height are the image's dimensions, not the length of
data.
Inputs
| Input | Description |
|---|---|
tick |
Publishes one frame. Wire to dora/timer/millis/N; the node stops when it closes. |
Environment variables
| Variable | Default | Meaning |
|---|---|---|
CAMERA_ID |
unset | Substring of a /dev/v4l/by-id/ entry. Wins over CAPTURE_PATH. |
CAPTURE_PATH |
0 |
Device path (/dev/video1) or index. A numeric string is an index. |
IMAGE_WIDTH |
native | Requested capture width; frames are also resized to it. |
IMAGE_HEIGHT |
native | Requested capture height; frames are also resized to it. |
ENCODING |
bgr8 |
One of bgr8, rgb8, yuv420, jpeg/jpg/jpe, png, bmp, webp. |
JPEG_QUALITY |
95 |
Quality 0-100, used only by the JPEG encodings. |
FLIP |
unset | VERTICAL, HORIZONTAL or BOTH. |
PREVIEW |
unset | true opens a window of the published frames; q stops the node. |
CAPTURE_FRAMES |
0 |
Stop after this many frames. 0 runs until the tick closes. |
Resizing only happens when both IMAGE_WIDTH and IMAGE_HEIGHT are set.
CAMERA_ID is worth preferring on a robot: a by-id name is stable across reboots and
across which USB port the camera is in, and an index is not.
CI=true makes a failed read publish a labelled black frame instead of raising, which
is what lets the dataflow run on a machine with no camera. It is not a configuration
knob.
Build
uv sync
Every dependency ships prebuilt wheels for linux-x86_64, linux-aarch64 and macos-arm64, so the node installs with no system packages and no compiler.
Requirements: dora 1.0+ (verified with dora-cli 1.0.1), Python 3.11+, uv, and a
V4L2 camera. PREVIEW also needs a display. On a bare Linux image opencv-python needs
the libGL shared libraries (libgl1, libglib2.0-0), which it links at import time.
Test
uv run pytest
Unit tests over device resolution, encoding and the image struct; they need neither a
camera nor a dataflow. The headless dataflow.yml run covers the wiring and the event
loop.
Camera selection on other platforms
Selecting by CAMERA_ID reads /dev/v4l/by-id/, so it is Linux only. Upstream also
enumerates cameras through macOS system_profiler and Windows PowerShell; that is not
carried here. CAPTURE_PATH works everywhere.