What is the color threshold value for the white color?

Question

My question is about color tracking... What is the color threshold value for white in python ? I need to track the white color alone in a group of pictures. So I need to separate the white color. In order to do so I need to know the threshold value of white color...

Answer 1

It depends on your pictures. Assuming that you're going to threshold using the RGB values, the RGB value for white is (255, 255, 255). But this value holds true for pure white color. If you have real-world pictures, you might have clearly white color at certain areas in your image but they wouldn't have the value (225, 255, 255). Factors like the shadow, lighting conditions, angle etc. contribute to the variance from pure white color value.

In order to threshold correctly, you need to check the range of values for your set of pictures. I recently worked on a similar problem and for my case, the range of values was as follows:

• Red channel: 200-255
• Green channel: 180-255
• Blue channel: 140-255

But please note that this accepts a lot of variation of white like light yellow. It will highly depend on your case so make sure you check the range on your data.

One way of that can be by displaying/showing your image using skimage and then hovering over white areas, it will display the RGB value on the bottom right corner of the image. Here is the code for showing an image in skimage:

from skimage import io
def show(img):
    io.imshow(img)
    io.show()

You can create a range of values/threshold from the values you notice this way.