counting pixel for UV powder image.

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Chinwendu Moghalu
Chinwendu Moghalu on 14 Aug 2020
Answered: Madhav Thakker on 20 Aug 2020
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
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Chinwendu Moghalu
Chinwendu Moghalu on 16 Aug 2020
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
Image Analyst on 16 Aug 2020
You attached a screenshot. Attach the original image, not a screenshot and not something that has been passed through Whats App.

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Answers (1)

Madhav Thakker
Madhav Thakker on 20 Aug 2020
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)

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