558 lines
22 KiB
Markdown
558 lines
22 KiB
Markdown
[//]: # (title: Detect people with a RaspberryPi, a thermal camera, Platypush and Tensorflow)
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[//]: # (description: Use cheap components and open-source software to build a robust presence detector.)
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[//]: # (image: /img/people-detect-1.png)
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[//]: # (author: Fabio Manganiello <fabio@platypush.tech>)
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[//]: # (published: 2019-09-27)
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Triggering events based on the presence of people has been the dream of many geeks and DIY automation junkies for a
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while. Having your house to turn the lights on or off when you enter or exit your living room is an interesting
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application, for instance. Most of the solutions out there to solve these kinds of problems, even more high-end
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solutions like the [Philips Hue sensors](https://www2.meethue.com/en-us/p/hue-motion-sensor/046677473389), detect
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motion, not actual people presence — which means that the lights will switch off once you lay on your couch like a
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sloth. The ability to turn off music and/or tv when you exit the room and head to your bedroom, without the hassle of
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switching all the buttons off, is also an interesting corollary. Detecting the presence of people in your room while
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you’re not at home is another interesting application.
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Thermal cameras coupled with deep neural networks are a much more robust strategy to actually detect the presence of
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people. Unlike motion sensors, they will detect the presence of people even when they aren’t moving. And unlike optical
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cameras, they detect bodies by measuring the heat that they emit in the form of infrared radiation, and are therefore
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much more robust — their sensitivity doesn’t depend on lighting conditions, on the position of the target, or the
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colour. Before exploring the thermal camera solution, I tried for a while to build a model that instead relied on
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optical images from a traditional webcam. The differences are staggering: I trained the optical model on more than ten
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thousands 640x480 images taken all through a week in different lighting conditions, while I trained the thermal camera
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model on a dataset of 900 24x32 images taken during a single day. Even with more complex network architectures, the
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optical model wouldn’t score above a 91% accuracy in detecting the presence of people, while the thermal model would
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achieve around 99% accuracy within a single training phase of a simpler neural network. Despite the high potential,
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there’s not much out there in the market — there’s been some research work on the topic (if you google “people detection
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thermal camera” you’ll mostly find research papers) and a few high-end and expensive products for professional
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surveillance. In lack of ready-to-go solutions for my house, I decided to take on my duty and build my own solution —
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making sure that it can easily be replicated by anyone.
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## Prepare the hardware
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For this example we'll use the following hardware:
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- A RaspberryPi (cost: around $35). In theory any model should work, but it’s probably not a good idea to use a
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single-core RaspberryPi Zero for machine learning tasks — the task itself is not very expensive (we’ll only use the
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Raspberry for doing predictions on a trained model, not to train the model), but it may still suffer some latency on a
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Zero. Plus, it may be really painful to install some of the required libraries (like Tensorflow or OpenCV) on
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the `arm6` architecture used by the RaspberryPi Zero. Any better performing model (from RPi3 onwards) should
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definitely do the job.
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- A thermal camera. For this project, I’ve used the
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[MLX90640](https://shop.pimoroni.com/products/mlx90640-thermal-camera-breakout) Pimoroni breakout camera (cost: $55),
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as it’s relatively cheap, easy to install, and it provides good results. This camera comes in standard (55°) and
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wide-angle (110°) versions. I’ve used the wide-angle model as the camera monitors a large living room, but take into
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account that both have the same resolution (32x24 pixels), so the wider angle comes with the cost of a lower spatial
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resolution. If you want to use a different thermal camera there’s not much you’ll need to change, as long as it comes
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with a software interface for RaspberryPi and
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it’s [compatible with Platypush](https://platypush.readthedocs.io/en/latest/platypush/plugins/camera.ir.mlx90640.html).
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Setting up the MLX90640 on your RaspberryPi if you have a Breakout Garden it’s easy as a pie. Fit the Breakout Garden on
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top of your RaspberryPi. Fit the camera breakout into an I2C slot. Boot the RaspberryPi. Done. Otherwise, you can also
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connect the device directly to the [RaspberryPi I2C interface](https://radiostud.io/howto-i2c-communication-rpi/),
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either using the right hardware PINs or the software emulation layer.
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## Prepare the software
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I tested my code on Raspbian, but with a few minor modifications it should be easily adaptable to any distribution
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installed on the RaspberryPi.
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The software support for the thermal camera requires a bit of work. The MLX90640 doesn’t come (yet) with a Python
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ready-to-use interface, but a [C++ open-source driver is provided](https://github.com/pimoroni/mlx90640-library) -
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and that's the driver that is wrapped by the Platypush integration. Instructions to install it:
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```shell
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# Install the dependencies
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[sudo] apt-get install libi2c-dev
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# Enable the I2C interface
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echo dtparam=i2c_arm=on | sudo tee -a /boot/config.txt
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# It's advised to configure the SPI bus baud rate to
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# 400kHz to support the higher throughput of the sensor
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echo dtparam=i2c1_baudrate=400000 | sudo tee -a /boot/config.txt
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# A reboot is required here if you didn't have the
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# options above enabled in your /boot/config.txt
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[sudo] reboot
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# Clone the driver's codebase
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git clone https://github.com/pimoroni/mlx90640-library
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cd mlx90640-library
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# Compile the rawrgb example
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make clean
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make bcm2835
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make I2C_MODE=LINUX examples/rawrgb
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```
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If it all went well you should see an executable named `rawrgb` under the `examples` directory. If you run it you should
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see a bunch of binary data — that’s the raw binary representation of the frames captured by the camera. Remember where
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it is located or move it to a custom bin folder, as it’s the executable that platypush will use to interact with the
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camera module.
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This post assumes that you have already installed and configured Platypush on your system. If not, head to my post on
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[getting started with Platypush](https://blog.platypush.tech/article/Ultimate-self-hosted-automation-with-Platypush),
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the [readthedocs page](https://platypush.readthedocs.io/en/latest/), the
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[Gitlab page](https://git.platypush.tech/platypush/platypush) or
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[the wiki](https://git.platypush.tech/platypush/platypush/-/wikis/home).
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Install also the Python dependencies for the HTTP server, the MLX90640 plugin and Tensorflow:
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```shell
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[sudo] pip install 'platypush[http,tensorflow,mlx90640]'
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```
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Tensorflow may also require some additional dependencies installable via `apt-get`:
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```shell
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[sudo] apt-get install python3-numpy \
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libatlas-base-dev \
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libblas-dev \
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liblapack-dev \
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python3-dev \
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gfortran \
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python3-setuptools \
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python3-scipy \
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python3-h5py
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```
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Heading to your computer (we'll be using it for building the model that will be used on the RaspberryPi), install
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OpenCV, Tensorflow and Jupyter and my utilities for handling images:
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```shell
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# For image manipulation
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[sudo] pip install opencv
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# Install Jupyter notebook to run the training code
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[sudo] pip install jupyterlab
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# Then follow the instructions at https://jupyter.org/install
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# Tensorflow framework for machine learning and utilities
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[sudo] pip install tensorflow numpy matplotlib
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# Clone my repository with the image and training utilities
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# and the Jupyter notebooks that we'll use for training.
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git clone https://github.com/BlackLight/imgdetect-utils ~/projects/imgdetect-utils
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```
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## Capture phase
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Now that you’ve got all the hardware and software in place, it’s time to start capturing frames with your camera and use
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them to train your model. First, configure
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the [MLX90640 plugin](https://platypush.readthedocs.io/en/latest/platypush/plugins/camera.ir.mlx90640.html) in your
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Platypush configuration file (by default, `~/.config/platypush/config.yaml`):
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```yaml
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# Enable the webserver
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backend.http:
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enabled: True
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camera.ir.mlx90640:
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fps: 16 # Frames per second
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rotate: 270 # Can be 0, 90, 180, 270
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rawrgb_path: /path/to/your/rawrgb
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```
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Restart the service, and if you haven't already create a user from the web interface at `http://your-rpi:8008`. You
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should now be able to take pictures through the API:
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```yaml
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curl -XPOST -H 'Content-Type: application/json' -d '
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{
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"type":"request",
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"action":"camera.ir.mlx90640.capture",
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"args": {
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"output_file":"~/snap.png",
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"scale_factor":20
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}
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}' -u 'username:password' http://localhost:8008/execute
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```
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If everything went well, the thermal picture should be stored under `~/snap.png`. In my case it looks like this while
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I’m in standing front of the sensor:
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Notice the glow at the bottom-right corner — that’s actually the heat from my RaspberryPi 4 CPU. It’s there in all the
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images I take, and you may probably see similar results if you mounted your camera on top of the Raspberry itself, but
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it shouldn’t be an issue for your model training purposes.
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If you open the web panel (`http://your-host:8008`) you’ll also notice a new tab, represented by the sun icon, that you
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can use to monitor your camera from a web interface.
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You can also monitor the camera directly outside of the webpanel by pointing your browser to
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`http://your-host:8008/camera/ir/mlx90640/stream?rotate=270&scale_factor=20`.
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Now add a cronjob to your `config.yaml` to take snapshots every minute:
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```yaml
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cron.ThermalCameraSnapshotCron:
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cron_expression: '* * * * *'
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actions:
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- action: camera.ir.mlx90640.capture
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args:
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output_file: "${__import__(’datetime’).datetime.now().strftime(’/home/pi/datasets/people_detect/images/%Y-%m-%d_%H-%M-%S.jpg’)}"
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grayscale: true
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```
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Or directly as a Python script under e.g. `~/.config/platypush/thermal.py` (make sure that `~/.config/platypush/__init__.py` also exists so the folder is recognized as a Python module):
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```python
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from datetime import datetime
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from platypush.cron import cron
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from platypush.utils import run
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@cron('* * * * *')
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def take_thermal_picture(**context):
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run('camera.ir.mlx90640.capture', grayscale=True,
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output_file=datetime.now().strftime('/home/pi/datasets/people_detect/images/%Y-%m-%d_%H-%m-%S.jpg'))
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```
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The images will be stored under `/home/pi/datasets/people_detect/images` (make sure that the directory exists before starting
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the service) in the format `YYYY-mm-dd_HH-MM-SS.jpg`. No scale factor is applied — even if the images will be tiny we’ll
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only need them to train our model. Also, we’ll convert the images to grayscale — the neural network will be lighter and
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actually more accurate, as it will only have to rely on one variable per pixel without being tricked by RGB
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combinations.
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Restart Platypush and verify that every minute a new picture is created under
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your images directory. Let it run for a few hours or days until you’re happy
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with the number of samples. Try to balance the numbers of pictures with no
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people in the room and those with people in the room, trying to cover as many
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cases as possible — e.g. sitting, standing in different points of the room etc.
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As I mentioned earlier, in my case I only needed less than 1000 pictures with
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enough variety to achieve accuracy levels above 99%.
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## Labelling phase
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Once you’re happy with the number of samples you’ve taken, copy the images over
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to the machine you’ll be using to train your model (they should be all small
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JPEG files weighing under 500 bytes each). Copy them to your local machine:
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```shell
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BASEDIR=~/datasets/people_detect
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mkdir -p "$BASEDIR"
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# Copy the images
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scp -r pi@raspberry:/home/pi/datasets/people_detect ~
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IMGDIR="$BASEDIR/images"
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# This directory will contain the raw numpy training
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# data parsed from the images (useful if you want to
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# re-train the model without having to reprocess all
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# the images)
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DATADIR="$BASEDIR/data"
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mkdir -p "$IMGDIR"
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mkdir -p "$DATADIR"
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# Create the labels for the images. Each label is a
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# directory under $IMGDIR
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mkdir "$IMGDIR/negative"
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mkdir "$IMGDIR/positive"
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```
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Once the images have been copied, and the directories for the labels created,
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run the `label.py` script provided in the repository to interactively label the
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images:
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```shell
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UTILS_DIR=~/projects/imgdetect-utils
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cd "$UTILS_DIR"
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python utils/label.py -d "$IMGDIR" --scale-factor 10
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```
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Each image will open in a new window and you can label it by typing either 1
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(negative) or 2 (positive) - the label names are gathered from the names of the
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directories you created at the previous step:
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At the end of the procedure the `negative` and `positive` directories under the
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images directory should have been populated.
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## Training phase
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Once we’ve got all the labelled images it’s time to train our model. A
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[`train.ipynb`](https://github.com/BlackLight/imgdetect-utils/blob/master/notebooks/ir/train.ipynb)
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Jupyter notebook is provided under `notebooks/ir` and it should be
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relatively self-explanatory:
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```python
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import os
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import numpy as np
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import matplotlib.pyplot as plt
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import tensorflow as tf
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from tensorflow import keras
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from tensorflow.keras.preprocessing.image import ImageDataGenerator
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# Define the dataset directory - replace it with the path on your local
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# machine where you have stored the previously labelled dataset.
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dataset_dir = os.path.join(os.path.expanduser('~'), 'datasets', 'people_detect')
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# Define the size of the input images. In the case of an
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# MLX90640 it will be (24, 32) for horizontal images and
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# (32, 24) for vertical images
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image_size = (32, 24)
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# Image generator batch size
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batch_size = 64
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# Number of training epochs
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epochs = 5
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# Instantiate a generator that puts 30% of the images into the validation set
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# and normalizes their pixel values between 0 and 1
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generator = ImageDataGenerator(rescale=1./255, validation_split=0.3)
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train_data = generator.flow_from_directory(dataset_dir,
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target_size=image_size,
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batch_size=batch_size,
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subset='training',
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class_mode='categorical',
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color_mode='grayscale')
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test_data = generator.flow_from_directory(dataset_dir,
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target_size=image_size,
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batch_size=batch_size,
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subset='validation',
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class_mode='categorical',
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color_mode='grayscale')
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```
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After initializing the generators, let's take a look at a sample of 25 images from the training set together with their
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labels:
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```python
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index_to_label = {
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index: label
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for label, index in train_data.class_indices.items()
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}
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plt.figure(figsize=(10, 10))
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batch = train_data.next()
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for i in range(min(25, len(batch[0]))):
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img = batch[0][i]
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label = index_to_label[np.argmax(batch[1][i])]
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plt.subplot(5, 5, i+1)
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plt.xticks([])
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plt.yticks([])
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plt.grid(False)
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# Note the np.squeeze call - matplotlib can't
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# process grayscale images unless the extra
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# 1-sized dimension is removed.
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plt.imshow(np.squeeze(img))
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plt.xlabel(label)
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plt.show()
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```
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You should see an image like this:
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Let's now declare a model and train it on the given training set:
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```python
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model = keras.Sequential([
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# Layer 1: flatten the input images
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keras.layers.Flatten(input_shape=image_size),
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# Layer 2: fully-connected layer with 80% the neurons as the input images
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# and RELU activation function
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keras.layers.Dense(round(0.8 * image_size[0] * image_size[1]),
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activation=tf.nn.relu),
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# Layer 2: fully-connected layer with 30% the neurons as the input images
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# and RELU activation function
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keras.layers.Dense(round(0.3 * image_size[0] * image_size[1]),
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activation=tf.nn.relu),
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# Layer 3: fully-connected layer with as many units as the output labels
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# and Softmax activation function
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keras.layers.Dense(len(train_data.class_indices),
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activation=tf.nn.softmax)
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])
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# Compile the model for classification, use the Adam optimizer and pick
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# accuracy as optimization metric
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model.compile(loss='categorical_crossentropy',
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optimizer='adam',
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metrics=['accuracy'])
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# Train the model in batches
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history = model.fit(
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train_data,
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steps_per_epoch=train_data.samples/batch_size,
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validation_data=test_data,
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validation_steps=test_data.samples/batch_size,
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epochs=epochs
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)
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# Example output:
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# Epoch 1/5 loss: 0.2529 - accuracy: 0.9196 - val_loss: 0.0543 - val_accuracy: 0.9834
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# Epoch 2/5 loss: 0.0572 - accuracy: 0.9801 - val_loss: 0.0213 - val_accuracy: 0.9967
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# Epoch 3/5 loss: 0.0254 - accuracy: 0.9915 - val_loss: 0.0080 - val_accuracy: 1.0000
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# Epoch 4/5 loss: 0.0117 - accuracy: 0.9979 - val_loss: 0.0053 - val_accuracy: 0.9967
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# Epoch 5/5 loss: 0.0058 - accuracy: 1.0000 - val_loss: 0.0046 - val_accuracy: 0.9983
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```
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We can now see how the accuracy of the model progressed over the iteration:
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```python
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epochs = history.epoch
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accuracy = history.history['accuracy']
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fig = plt.figure()
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plot = fig.add_subplot()
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plot.set_xlabel('epoch')
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plot.set_ylabel('accuracy')
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plot.plot(epochs, accuracy)
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```
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The output should look like this:
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By constraining the problem properly (i.e. translating "detect people in an image" to "infer the presence of people by
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telling if there are more white halos than usual in a small grayscale image") we have indeed managed to achieve high
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levels of accuracy both on the training and validation set despite using a relatively small dataset.
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## Deploying the model
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Once you are happy with the model, it's time to save it so it can be deployed to your RaspberryPi for real-time
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predictions:
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```python
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def model_save(model, target, labels=None, overwrite=True):
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import json
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import pathlib
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# Check if we should save it like a .h5/.pb file or as a directory
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model_dir = pathlib.Path(target)
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if str(target).endswith('.h5') or \
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str(target).endswith('.pb'):
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model_dir = model_dir.parent
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# Create the model directory if it doesn't exist
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pathlib.Path(model_dir).mkdir(parents=True, exist_ok=True)
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# Save the Tensorflow model using the .save method
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model.save(target, overwrite=overwrite)
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# Save the label names of your model in a separate JSON file
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if labels:
|
||
labels_file = os.path.join(model_dir, 'labels.json')
|
||
with open(labels_file, 'w') as f:
|
||
f.write(json.dumps(list(labels)))
|
||
|
||
model_dir = os.path.expanduser('~/models/people_detect')
|
||
model_save(model, model_dir,
|
||
labels=train_data.class_indices.keys(), overwrite=True)
|
||
```
|
||
|
||
If you managed to execute the whole notebook then you’ll have your model saved under `~/models/people_detect`.
|
||
You can now copy it over to the RaspberryPi and use it to do predictions (first create `~/models` on the RaspberryPi
|
||
if it's not available already):
|
||
|
||
```shell
|
||
scp -r ~/models/people_detect pi@raspberry:/home/pi/models
|
||
```
|
||
|
||
## Detect people in the room
|
||
|
||
Once the Tensorflow model has been deployed to the RaspberryPi you can quickly test how it performs against some
|
||
pictures taken on the device using
|
||
the [`tensorflow.predict`](https://platypush.readthedocs.io/en/latest/platypush/plugins/tensorflow.html#platypush.plugins.tensorflow.TensorflowPlugin.predict)
|
||
method:
|
||
|
||
```shell
|
||
curl -XPOST -u 'user:pass' -H 'Content-Type: application/json' -d '
|
||
{
|
||
"type":"request",
|
||
"action":"tensorflow.predict",
|
||
"args": {
|
||
"inputs": "~/datasets/people_detect/positive/some_image.jpg",
|
||
"model": "~/models/people_detect"
|
||
}
|
||
}' http://your-raspberry-pi:8008/execute
|
||
```
|
||
|
||
Expected output:
|
||
|
||
```json
|
||
{
|
||
"id": "<response-id>",
|
||
"type": "response",
|
||
"target": "http",
|
||
"origin": "raspberrypi",
|
||
"response": {
|
||
"output": {
|
||
"model": "~/models/people_detect",
|
||
"outputs": [
|
||
{
|
||
"negative": 0,
|
||
"positive": 1
|
||
}
|
||
],
|
||
"predictions": [
|
||
"positive"
|
||
]
|
||
},
|
||
"errors": []
|
||
}
|
||
}
|
||
```
|
||
|
||
Once the structure of the response is clear, we can replace the previous cronjob that stores pictures at regular
|
||
intervals with a new one that captures pictures and feeds them to the previously trained model to make predictions (I'll
|
||
use a Python script stored under `~/.config/platypush/scripts` in this case, but it will also work with a cron defined
|
||
in YAML in `config.yaml`) and, for example, turns on the lights when presence is detected and turns them off when
|
||
presence is no longer detected (I'll use
|
||
the [`light.hue`](https://platypush.readthedocs.io/en/latest/platypush/plugins/light.hue.html) plugin in this example):
|
||
|
||
```python
|
||
import os
|
||
from platypush.context import get_plugin
|
||
from platypush.cron import cron
|
||
|
||
|
||
@cron('* * * * * */30')
|
||
def check_presence(**context):
|
||
# Get plugins by name
|
||
camera = get_plugin('camera.ir.mlx90640')
|
||
tensorflow = get_plugin('tensorflow')
|
||
lights = get_plugin('light.hue')
|
||
|
||
image_file = '/tmp/frame.jpg'
|
||
model_file = os.path.expanduser('~/models/people_detect/saved_model.h5')
|
||
camera.capture_image(
|
||
image_file=image_file, grayscale=True)
|
||
|
||
prediction = tensorflow.predict(
|
||
inputs=image_file, model=model_file)['predictions'][0]
|
||
|
||
if prediction == 'positive':
|
||
lights.on()
|
||
else:
|
||
lights.off()
|
||
```
|
||
|
||
Restart the service and let it run. Every 30 seconds the cron will run, take a picture, check if people are detected in
|
||
that picture and turn the lights on/off accordingly.
|
||
|
||
## What's next?
|
||
|
||
That’s your call! Feel free to experiment with more elaborate rules, for example to change the status of the music/video
|
||
playing in the room when someone enters, using Platypush media plugins. Or say a custom good morning text when you first
|
||
enter the room in the morning. Or build your own surveillance system to track the presence of people when you’re not at
|
||
home. Or enhance the model to detect also the number of people in the room, not only the presence. Or you can combine it
|
||
with an optical flow sensor, distance sensor, laser range sensor or optical camera (platypush provides plugins for many
|
||
of them) to build an even more robust system that also detects and tracks movements or proximity to the sensor, and so
|
||
on.
|