🌟 Constellano: Star recognition algorithm 🌌 💻

An app written in Python (Flask) that enables you to recognize 👀 constellations on a static picture, using HAAR cascade 🤖.

1. Prerequisite ⚙️

To run this app you'll need to install python 3.10.x.

2. How to run? 🚀

Clone the repo using the following command:

git clone git@github.com:marinmaslov/constellano.git

Position yourself into the constellano directory:

cd constellano

Create a virtual environment:

python -m venv venv

Install all required dependencies:

pip install -r requirements.txt

Activate it:

source venv/bin/activate

Install all required modules (make sure you're is the same directory where the requirements.txt file is):

pip install -r requirements.txt

Run the app with the following command (again make sure you're in the same directory as the app.py file):

flask run

3. What's inside? 🧐

A quick look at the apps files and directories.

.
├── cascades
|       |── pretrained_001.xml
|       |── ...
|       └── pretrained_NNN.xml
├── data
|       |── negatives
|       └── positives
├── scripts
|       └── all scripts explained in section 4.
├── testing
|       └── mostly testing images
├── .gitignore
├── Procfile
├── README.md
├── app.py
├── requirements.txt
└── runtime.txt

4. Documentation 📚

4.1. Introduction

In this section an overview on how to use all the scripts to prepare data and train HAAR to detect the input object will be explained.

4.2. Data preparation

4.2.1. Stellarium scripts

Fisrtly, we need to collect our data. Instead of shooitng the sky and waisting hundreds of hours on it, we'll use "laboratory" data which we'll fetch from an open-source software called Stellarium. A detailed approach on how to import and run scripts in Stellraium can be found here!

We have two scripts: one for fetching positive images (the ones containing the object we want to be able to detect) and one for fetching negative images (all other parts of the sky without that object), which can be found in scripts/

Script for fetching positives

Before running this script, a few constants should be changed.

• DESTINATION_PATH represents the system path where the images will be stored
• RA_TARGET_START starting RA coordinate (in decimal degrees) for the object of interest
• RA_TARGET_END ending RA coordinate (in decimal degrees) for the object of interest
• DEC_TARGET_START starting DEC coordinate (in decimal degrees) for the object of interest
• DEC_TARGET_END ending DEC coordinate (in decimal degrees) for the object of interest

After running this script you'll end up with a few (max. 30) images that contain the object of interest.

Script for fetching negatives

This script will take screen shoots of the whole sky, just change the following constant.

• DESTINATION_PATH represents the system path where the images will be stored

After running this script you'll end up with more then 10k images of the sky.

4.2.2. Star detection

The first step is to apply star masks onto the brightest stars in the positive images. To apply the star masks run the script scripts/StarDetector.py as follows:

py scripts/StarDetector.py --images PATH_TO_IMAGES_DIR --masksize MASK_SIZE_PERCENTAGE --outputname OUTPUT_NAME --percision PERCISION_PERCENTAGE

The parameters are:

• PATH_TO_IMAGES_DIR relative path to the directory containing the positive images
• MASK_SIZE_PERCENTAGE mask size percentage in realtion to the input image's width (e.g. 0.06 means 6% × input image's width)
• OUTPUT_NAME name that will be given to the output files
• PERCISION_PERCENTAGE percentage of the brightest star that will be used as the a thrashold value. To all the stars having an area size smaller then the threshold value won't be covered by the mask. Usage is similar to MASK_SIZE_PERCENTAGE (e.g. 0.18 means 18%)

4.2.3. Image cropping

After successfully appyling masks onto stars crop the image so only the object of interest will be visible.

4.2.4. Resizer

The next step is to resize all images to some desired dimensions (e.g. 500×500px).

Run the script as follows:

py scripts/Resizer.py --images PATH_TO_IMAGES_DIR --size SIZE --grayscale VALUE

The parameters are:

• PATH_TO_IMAGES_DIR relative path to the directory containing the cropped positive images
• SIZE size in pixels (size × size) for the output images
• VALUE if images need to be converted to grayscale set 0, if not set to any other number

4.2.4. Generating more positive samples

This step will generate many new positive images (with distorsions) that will be used to train the cascade. The new images are generated by applying the exisitng positive images onto the negative images but with distorisions.

As this script uses the openCV library as a system module, please install openCV as a system module (perhaps the best is to run it on Linux as it is the easiest to install openCV as a system module there).

Run the script as follows:

python scripts/PrepareSamples.py --pos POSITIVES_DIR --neg NEGATIVES_DIR --num NUMBER_OF_NEW --maxxangle MAX_X_ANGLE --maxyangle MAX_Y_ANGLE --maxzangle MAX_Z_ANGLE

The parameters are:

• POSITIVES_DIR relative path to the directory containing the positive images
• NEGATIVES_DIR relative path to the directory containing the negative images
• NUMBER_OF_NEW number of positives that will be genmerated for each existing positive
• MAX_X_ANGLE the max. angle on the x-axis the positives will be rotated while appyling them on the negatives (best opetion 0.0)
• MAX_Y_ANGLE the max. angle on the y-axis the positives will be rotated while appyling them on the negatives (best opetion 0.0)
• MAX_Z_ANGLE the max. angle on the z-axis the positives will be rotated while appyling them on the negatives (best opetion 0.0)

After executing this script a directory named final_samples will be created containing all new positive images and the final_samples.txt file needed for the newx step. Also two files named positives.txt and negatives.txt will appear.

4.2.5. Generating the HAAR vector

To generate the input vector for the HAAR training, run the following openCV command:

opencv_createsamples -info SAMPLES_LIST -num NUMBER -w WIDTH -h HEIGHT -vec VECOTR -maxxangle MAX_X_ANGLE -maxyangle MAX_Y_ANGLE -maxzangle MAX_Z_ANGLE

The parameters are:

• SAMPLES_LIST list file (.txt) with all positive samples (final_samples/final_samples.txt from last step)
• NUMBER number of positive images that will be used for the creation of the vector file
• WIDTH width of the input images (last step used 24)
• HEIGHT height of the input images (last step used 24)
• VECOTR name of the output vector file (e.g. positives.vec)
• MAX_X_ANGLE the max. angle on the x-axis the positives have been rotated
• MAX_Y_ANGLE the max. angle on the y-axis the positives have been rotated
• MAX_Z_ANGLE the max. angle on the z-axis the positives have been rotated

4.3. HAAR training

After preparing all input files for the HAAR training process, hit the following command:

opencv_traincascade -data DATA -vec VECOTR -bg NEGATIVES_LIST -numPos NUMBER_POS -numNeg NUMBER_NEG -numStages NUMBER_STAGES -width WIDTH -height HEIGHT -mode ALL -bt DAB -minHitRate 0.995 -maxFalseAlarmRate 0.5 -maxWeakCount 100 -maxDepth 1 -precalcValBufSize 1024 -precalcIdxBufSize 1024

The parameters are:

• DATA directory with final samples from last steps
• VECOTR vector file from last step
• NEGATIVES_LIST negatives list from last step (negatives.txt)
• NUMBER_POS number of positive images that will be used to train the cascade
• NUMBER_NEG number of negative images that will be used to train the cascade
• NUMBER_STAGES number of stages HAAR will take to train the cascade (min. 1, max. 20)
• WIDTH width of the input images (last step used 24)
• HEIGHT height of the input images (last step used 24)

Other parameters should be kept as they are.

After the training finishes, an output file named cascade.xml will be created in the directory final_samples/.

4.4. Detecting objects using the generated HAAR cascade

The HAAR detection script can be run using the following command:

python scripts/HaarDetection.py --images IMAGES_DIR --masksizeMin MASK_SIZE_MIN --masksizeMax MASK_SIZE_MAX --outputname OUTPUT_NAME --percisionMin PERCISION_MIN --percisionMax PERCISION_MAX --cascade CASCADES_DIR --scale 1.01 --minNghb 2 --json JSON_FILE --plot 0 --streach 0

The parameters are:

• IMAGES_DIR path to dircetory containing the input images on which you want to detect objects
• MASK_SIZE_MIN minimum mask size in percentage as described in 4.2.2.
• MASK_SIZE_MAX maximum mask size in percentage as described in 4.2.2.
• OUTPUT_NAME name of the output directory and files
• PERCISION_MIN minimum percision in percentage as described in 4.2.2. (preferably 0.0)
• PERCISION_MAX maximum percision in percentage as described in 4.2.2.
• CASCADES_DIR directory containing all the cascade files (the output files from step 4.3. should be placed into this directory and renamed to the desired name of the object question)
• JSON_FILE path to the json file

Other parameters should be as they are. If detection is unsucessful change the streach parameter to 1, if you want to plot every image in every step of the detectio script change the plot parameter to 1.

"The real friends of the space voyager are the stars. Their friendly, familiar patterns are constant companions, unchanging, out there." - James Lovell, Apollo Astronaut

Python Script created by Marin Maslov @ FESB (UNIST)