I have a black and white image, how can I find the area percentage of the black areas?

I have this black and white image. What I need is the percentage of the black areas. I first change the contrast so the black and white areas are more distinguishable. but I don’t know how to proceed from here. I'd appreciate if someone let me know which function(s) I should use.

Answer 1

[Matt J]

Assuming you've "binarized" the image, so that black=0 and white=1,

percentageBlack=(1-nnz(image)/numel(image))*100

[Ali Amiri]

Thank you very much for your quick response. This is my code so far, I am assuming I have a binary image:

I = imread('CT2.tif') ;
figure; imshow(I)

BW = im2bw(I,0.4);
figure, imshow(BW)

percentageBlack=(1-nnz(BW)/numel(BW))*100

[Matt J]

Looks like you're done!

[Ali Amiri]

Thank you for your help and great answer!

[AMAR P]

Thanks, This quite optimizes time too...

[Shashank]

Could you please tell how to find the actual area of the black region alone? Thanks

[Matt J]

 numel(image)-nnz(image);

[Shashank]

Worked. Thanks a lot!!