counting pixel for UV powder image.

I am conducting an experiment using uv powder, I took a picture to upload using imagej. This is all sp new to me. the file would not upload directly. evetually I was able to by first downlaoding it from whatsapp.

I changed it to greyscale and then to binary. I tried to set a threshold for the pixle but i do not know how to, and continue to make a mess of it. I do not know how to process the data or determine how to count the pixel. This is the image after i had croped and converted it to grey scale

This

[Image Analyst]

Zip up the file and attach it. What format is it in? Is it not a TIFF, BMP, PNG, or JPG image? What do you want to find out from that image you posted? I don't see anything obvisous. See my File Exchange for an interactive thresholding program.

[Chinwendu Moghalu]

what file exchange are you refering to?

I am supposed to count the pixles, and determine distribution of the UV powder. Then have the distribution in %. after this I will compare the different results to see which fabric has the most transfer of uv powder and also persistence after wash.

this was the result i got from doing random things and then running a test

[Image Analyst]

See my File Exchange for a interactive thresholding app: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862&sort=downloads_desc

You attached a screenshot. Attach the original image, not a screenshot and not something that has been passed through Whats App.

Answer 1

[Madhav Thakker]

Hi

You can use imbinarize to create a binary image using different threshold values, by default it will calculate the threshold using Otsu's method.

After that on the binarize image, you can use nnz to count non-zero pixels and these values helps to determine the distribution of UV pixels. For example,

I = imread('uv.jpeg'); 
threshold = 0.5; 
binarized_image = imbinarize(I,threshold); 
non_zero_pixels = nnz(binarized_image); 
disp(non_zero_pixels) 

imbinarize MATLAB documentation - https://in.mathworks.com/help/images/ref/imbinarize.html