The average of an angle… (mean of Hue Value)

My solution to this issue was to write a bunch of code to handle the behavior of the average calculation at the 0 and 360 points. It was a pain in the neck, and I probably have it wrong :(.

Today I retook the issue and found various ways of doing the average calculation with less code and more math. This stack overflow link has really cool links and ideas. I really like the following algorithm to handle the calculation:

x = y = 0
foreach angle {
   x += cos(angle)
   y += sin(angle)
average_angle = atan2(y, x)

There is also a link on wikipedia briefly explaining stuff about means of circular quantities. Here is a paper on google docs that also talks about this issue.

I unfortunately did not find a way to do it with opencv. Which is strange given that you might want the mean of an HSV image. I guess the way to go is to convert it to RGB, calculate the mean and then try to use the RGB->HSV equations to find the Hue mean. However, this seems just plain wrong. Additionally the cv::mean functions do not provide (according to the documentation) a facility to differentiate between a regular Cartesian mean and an angular mean.


About joelgranados

I'm fascinated with how technology and science impact our reality and am drawn to leverage them in order to increase the potential of human activity.
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