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Remove background function can help you with focusing only on the main object. Offers two types of background removal (histogram and canny), and each can be useful for different kinds of images. The Canny background removal uses canny edge detector, dilation, and erosion.
Unifier
Unifies the position and angle of objects or just puts the angle of the object into Context (if this option is ticked). Remove background that needs to be used before Unifier and have the same background color selected.
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Can be used to reduce light shapes found in the input image. Details in the OpenCV documentation for erode and morphological transformations.
Polar transform
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