# Mono Preview

This example shows how to set up a pipeline that outputs the left and right grayscale camera images, connects over XLink to
transfer these to the host real-time, and displays both using OpenCV.

### Similar samples:

 * [RGB Preview](https://docs.luxonis.com/software/depthai/examples/rgb_preview.md)
 * [Depth Preview](https://docs.luxonis.com/software/depthai/examples/depth_preview.md)

## Demo

## Setup

Please run the [install script](https://github.com/luxonis/depthai-python/blob/main/examples/install_requirements.py) to download
all required dependencies. Please note that this script must be ran from git context, so you have to download the
[depthai-python](https://github.com/luxonis/depthai-python) repository first and then run the script

```bash
git clone https://github.com/luxonis/depthai-python.git
cd depthai-python/examples
python3 install_requirements.py
```

For additional information, please follow the [installation guide](https://docs.luxonis.com/software/depthai/manual-install.md).

## Source code

#### Python

```python
#!/usr/bin/env python3

import cv2
import depthai as dai

# Create pipeline
pipeline = dai.Pipeline()

# Define sources and outputs
monoLeft = pipeline.create(dai.node.MonoCamera)
monoRight = pipeline.create(dai.node.MonoCamera)
xoutLeft = pipeline.create(dai.node.XLinkOut)
xoutRight = pipeline.create(dai.node.XLinkOut)

xoutLeft.setStreamName('left')
xoutRight.setStreamName('right')

# Properties
monoLeft.setCamera("left")
monoLeft.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoRight.setCamera("right")
monoRight.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)

# Linking
monoRight.out.link(xoutRight.input)
monoLeft.out.link(xoutLeft.input)

# Connect to device and start pipeline
with dai.Device(pipeline) as device:

    # Output queues will be used to get the grayscale frames from the outputs defined above
    qLeft = device.getOutputQueue(name="left", maxSize=4, blocking=False)
    qRight = device.getOutputQueue(name="right", maxSize=4, blocking=False)

    while True:
        # Instead of get (blocking), we use tryGet (non-blocking) which will return the available data or None otherwise
        inLeft = qLeft.tryGet()
        inRight = qRight.tryGet()

        if inLeft is not None:
            cv2.imshow("left", inLeft.getCvFrame())

        if inRight is not None:
            cv2.imshow("right", inRight.getCvFrame())

        if cv2.waitKey(1) == ord('q'):
            break
```

#### C++

```cpp
#include <iostream>

// Includes common necessary includes for development using depthai library
#include "depthai/depthai.hpp"

int main() {
    // Create pipeline
    dai::Pipeline pipeline;

    // Define sources and outputs
    auto monoLeft = pipeline.create<dai::node::MonoCamera>();
    auto monoRight = pipeline.create<dai::node::MonoCamera>();
    auto xoutLeft = pipeline.create<dai::node::XLinkOut>();
    auto xoutRight = pipeline.create<dai::node::XLinkOut>();

    xoutLeft->setStreamName("left");
    xoutRight->setStreamName("right");

    // Properties
    monoLeft->setCamera("left");
    monoLeft->setResolution(dai::MonoCameraProperties::SensorResolution::THE_720_P);
    monoRight->setCamera("right");
    monoRight->setResolution(dai::MonoCameraProperties::SensorResolution::THE_720_P);

    // Linking
    monoRight->out.link(xoutRight->input);
    monoLeft->out.link(xoutLeft->input);

    // Connect to device and start pipeline
    dai::Device device(pipeline);

    // Output queues will be used to get the grayscale frames from the outputs defined above
    auto qLeft = device.getOutputQueue("left", 4, false);
    auto qRight = device.getOutputQueue("right", 4, false);

    while(true) {
        // Instead of get (blocking), we use tryGet (non-blocking) which will return the available data or None otherwise
        auto inLeft = qLeft->tryGet<dai::ImgFrame>();
        auto inRight = qRight->tryGet<dai::ImgFrame>();

        if(inLeft) {
            cv::imshow("left", inLeft->getCvFrame());
        }

        if(inRight) {
            cv::imshow("right", inRight->getCvFrame());
        }

        int key = cv::waitKey(1);
        if(key == 'q' || key == 'Q') {
            return 0;
        }
    }
    return 0;
}
```

## Pipeline

### Need assistance?

Head over to [Discussion Forum](https://discuss.luxonis.com/) for technical support or any other questions you might have.