# Webcam

> Show a live webcam in a Python desktop app with Pyzed — OpenCV or ffmpeg on Windows, macOS and Linux, snapshots, raw RGBA frames and a test pattern.

Source: https://albakore.github.io/pyzed/audio/components/webcam/

(Image: A webcam view with a recording badge showing the moving test pattern)

**In plain words:**

Put a camera's live picture in your window with one line. It opens the camera when it appears and
closes it when it goes away.

```python
ui.camera.Webcam(device=0, width=480, height=360, mirror=True)
```

## How frames arrive

The camera is read in a background thread. Every new frame asks the window to redraw, so the
view stays live without a timer and without slowing the rest of the app. Two `Webcam`s of the
same device share one capture.

The capture uses whichever of these is available, in this order (`backend="auto"`):

| Backend | Needs | Notes |
| --- | --- | --- |
| `"opencv"` | `pip install opencv-python` | The most compatible on every system. |
| `"ffmpeg"` | the `ffmpeg` program | Video4Linux on Linux, AVFoundation on macOS, DirectShow on Windows. |
| `"test"` | nothing | Moving color bars: for screenshots, tests and machines without a camera. |

## Using the frames

`pyzed.camera.Camera` gives you the frames to process (detect faces, measure brightness, record):

```python
from pyzed import camera

cam = camera.Camera(0, width=640, height=480, mirror=True)
cam.start()
frame = cam.read()             # waits for the next Frame(width, height, pixels, index, time)
cam.snapshot("photo.png")      # saved without Pillow
cam.on_frame.append(lambda f: print(f.index))   # runs in the camera thread
cam.stop()
```

`frame.pixels` are RGBA bytes (`width * height * 4`): `numpy.frombuffer(frame.pixels, "uint8")`
turns them into an array, and `pz.image(frame.pixels, size=(frame.width, frame.height))` draws
them. `camera.devices()` lists the cameras found.

| Property | Default | What it does |
| --- | --- | --- |
| `device` | `0` | Camera index, a path (`"/dev/video2"`) or, on Windows with ffmpeg, its name. |
| `camera` | `None` | A `Camera` of yours to show instead. |
| `width`, `height` | `320`, `240` | Size of the view. |
| `capture_width`, `capture_height`, `fps` | `640`, `480`, `30` | What to ask the camera for. |
| `mirror` | `True` | Flip it like a mirror. |
| `fit` | `"cover"` | `"cover"` crops to fill, `"contain"` shows it all. |
| `radius` | `8` | Rounded corners. |
| `overlay` | `True` | A badge with a recording dot and the frame rate. |
| `paused` | `False` | Freezes the last frame. |
| `backend` | `"auto"` | See above. |

**Caution:**

On macOS the first run asks for permission to use the camera; the program that runs Python
(Terminal, your editor) is the one that gets it.