Black color object detection HSV range in opencv

Question

What is the range of Black color object detection?

i tried following code

cvInRangeS(imgHSV, cvScalar(0, 0, 0, 0), cvScalar(0, 255, 255, 0), imgThreshold);

but its not working.

Solution 1

For black and white colors in HSV range you have to set hue at maximum range (0 to 180), and saturation at maximum range (0 to 255). You can play with the value, for example, 0 to 30 or 40 for black, and 200 to 255 for white.

// for black
cvInRangeS(imgHSV, cvScalar(0, 0, 0, 0), cvScalar(180, 255, 30, 0), imgThreshold);

// for white
cvInRangeS(imgHSV, cvScalar(0, 0, 200, 0), cvScalar(180, 255, 255, 0), imgThreshold);

Or you can use the C++ interface:

// for black
cv::inRange(imgHSV, cv::Scalar(0, 0, 0, 0), cv::Scalar(180, 255, 30, 0), imgThreshold);

// for white   
cv::inRange(imgHSV, cv::Scalar(0, 0, 200, 0), cv::Scalar(180, 255, 255, 0), imgThreshold);

Solution 2

Black colour in HSV and HSL colour space, is detected with low Value (or Lightness in HSL).

White colour in HSL detected with high Value. White colour is HSV detected with high Lightness and Low Saturation.

for white

cv::inRange(imgHSL, cv::Scalar(0, 0, 200, 0), cv::Scalar(180, 255, 255, 0), imgThreshold);

or

cv::inRange(imgHSV, cv::Scalar(0, 0, 200, 0), cv::Scalar(180, 20, 255, 0), imgThreshold);

Solution 3

Hue is like the dominant light wavelength your eye receives. But black light wavelength is beyond visible light wavelength range. The hue doesn't count black light directly.

Value is the lightness/darkness value. Any hue can be regarded as black in a bad lighting condition.

Saturation is also referred to as "chroma". It depicts the signal intensity level of any hue. If S=0, any hue looks like "black" in color. On the contrary, if you want to segment true black color (rather than the "black" triggered by "darkness") from images, set a small saturation threshold is always the first job. Then combine with Hue and Value masks as the secondary mask will give you a more accurate answer.

Comments

[sushma ahirwar]

Thank you all for your suggestion. cvInRangeS(imgHSV, cvScalar(0, 0, 0, 0), cvScalar(180, 255, 40, 0), imgThreshold); Its working fine for black.