How to isolate a single color in an image

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+1 Q:

How to isolate a single color in an image

I'm using the python OpenCV bindings and at the moment I try to isolate a colorrange. That means I want to filter out everything that is not reddish.

I tried to take only the red color channel but this includes the white spaces in the Image too.

What is a good way to do that?

+4 A:

Use a different color space: http://en.wikipedia.org/wiki/HSL_color_space

Dave 2009-06-09 05:41:02

How about using a formular like r' = r-(g+b)?

Niki 2009-06-09 05:45:06

PS: You can try any function on colors that has a maximum at RGB=(255,0,0). E.g. 255-Euclidian Distance(rgb, Red), or Euclidian Distance in a HSV color space.

Niki 2009-06-09 05:53:23

+1 A:

Use the HSV colorspace. Select pixels that have an H value in the range that you consider to contain "red," and an S value large enough that you do not consider it to be neutral, maroon, brown, or pink. You might also need to throw out pixels with low V's. The H dimension is a circle, and red is right where the circle is split, so your H range will be in two parts, one near 255, the other near 0.

Jive Dadson 2010-02-05 02:56:26

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How to isolate a single color in an image

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