# Changes

## Hough Circle Transform

, 18:17, 18 April 2017
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The plugin has two separate algorithms available:
'''Full Hough Transform: '''
This algorithm performs a full Hough circle transform on every frame. The algorithm then searches for the highest scoring circle first, then the second highest, and so on. When a circle is found, the Hough transform space is cleared out around the found circle to prevent the same circle from being found repeatedly. This parameter can be adjusted to allow for increasing degrees of overlap between neighboring circles.
'''Local Hough Transform: '''
This algorithm is designed for high-speed tracking of circles in a time-lapse series. The algorithm performs the full Hough circle transform on the first frame to find the initial radius and position of each circle. In subsequent frames, the algorithm then only performs a Hough transform near the centroid of each circle in subsequent frames. If the number of found circles drops below the minimum number of specified circles, the algorithm performs a full Hough circle transform on the next frame to try and find any circles missed in the local search.
====''Hough score threshold''====
This option sets the minimum cutoff for the Hough score (i.e. number ratio of votes) that a circle can have to count as a valid object. The search starts with This value is described as the highest scoring circle, and then the second highest, and so on, so if there are a greater following ratio: :$\text{Hough score}=\left ( \frac{\text{number of circles with a score above votes}}{\text{transform resolution}} \right )$Since the threshold than the limit set in "Maximum maximum number of circles to be found", only the highest scoring circles will be returned.  NOTE: When votes a circle can receive is the transform resolution is changed (see belowi.e. every transform resulted in a vote) , the scores will change tohighest score a circle can receive is 1.0. This is because Thus, the resolution sets lower the number of rounds of voting. Thereforescore threshold, as the number of voting rounds increases, more tolerant the score per object search will increase as wellbe of incomplete and/or imperfect circles.
====''Hough transform resolution''====
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