Testing Zernike moments a powerfull shape descriptor, based on Zernike polynomials

In mathematics, the Zernike polynomials are a sequence of polynomials that are orthogonal on the unit disk.

Image processing and computer vision techniques such as:

• Edge detection
• Thresholding
• Perspective warping

We can abstractly represent the image using only a list of numbers (image feature vector).

Python Libraries You Will Need:

• Requests
• BeautifulSoup (bs4 web scraping)
• NumPy
• SciPy
• Scikit-Image
• OpenCV (with bindings)

The steps:

1. Download images (build a dataset)
2. Extract features of the images in terms of their outline (the shape)
3. Process (extract features) a new image
4. Compare feature of the new image to the features of the dataset (using euclidean distance)

Image moments:

• Calculate the centroid (the center of the object, in terms of x, y coordinates);
• Calculate moments based on the contour of an image. The scaling and translation of the object in the image:
• Depending on where the object is translated in the image, moments will be different;
• Depending on how large or small (the object is scaled) in the image, moments will be different. To avoid descriptors with different values based on the translation and scaling:
• Perform segmentation the foreground from the background;
• Form a tight bounding box around the object and crop it out;
• Translation invariance!
• Resize the object to a constant NxM pixels;
• Scale invariance!
• The Zernike Moment is rotation invariant.

The steps of Execution:

1. python web_scraping_images_redblue.py or
2. python web_scraping_images_redblue.py -generation 2 or
3. python web_scraping_images_redblue.py -g 3 3.1. Download images and place in a folder: sprites\000Name.png
4. python indexing.py 4.1. Creates an index file of moments of all images: index.pkl
5. python find_screen.py --query screens\gameboy_marowak.jpg 5.1. Creates an image of the object that's found: object.png
6. python whos.py --index index.pkl --object object.png 6.1. Compare the object and print its name: The object is: 'Name'

Referenced: https://www.pyimagesearch.com/ by Adrian Rosebrock