bwarea & area, white/black ratio

Hi,

Can someone please explain me what is the difference of bwarea & area.

I have an image which is black and white (after segmentation and fill) & I wish to calculate the area of an object (as I understand done by bwarea) relative to the image area (imageArea = regionprops(image_name, 'Area')), more or less calculating the white/black ratio.

Any other ideas is welcome.

Thanks.

Answer 1

[Image Analyst]

They use different algorithms. regionprops gives the number of pixels while bwarea gives some kind of weighted area that depends on the shape of the boundary. This is described in the documentation for bwarea

The white to black ratio is

totalPixels = numel(binaryImages);
numWhitePixels = sum(binaryImage(:));
numBlackPixels = totalPixels - numWhitePixels;
ratio = numWhitePixels  / numBlackPixels;

Answer 2

[dan kin]

Hi,

Therefore, bwarea/area is not like white/black ratio. Am I correct?

If this is the case how do I solve it, built in function?

Thx

[Image Analyst]

You are correct. It is not the white to black ratio - it is an area in pixels.

[shivam sahil]

Hey! I want to implement the same code for RGB to get pixel count of particular rgb index, please guide me with the code for the same.

[Image Analyst]

See attached demo. Also see the function colorcloud().