extraction of part of image

hello,

i want to extract some part of original image bsed of pixel values. for example i want to extract part which have pixel values greater than 200 and other part to be blackened .i dont wanna use im crop bcoz the part i want to extract should depend on pixel values.

Answer 1

[Subhadeep Koley]

Hi Smruti, the below code might help as you want "to extract the part of original image based on pixel values the output will be same image with threshold 200 and other blacken".

Also you might want to use the Color Thresholder App.

img = imread('peppers.png');
[r, c, b] = size(img);
th_img = uint8(zeros(r,c,b));
th = 100; % Put your threshold here
for i = 1:r
    for j = 1:c
        if img(i, j, :) > th
            th_img(i, j, :) = img(i, j, :);
        end
    end
end
figure, imshowpair(img, th_img, 'montage');

Answer 2

[Bhaskar R]

im = imread('peppers.png');    % read image
res_image = uint8(im>200).*im;  % apply your condition
figure, imashow(res_image);

[Smruti Khobragade]

sir i m getting this error

"Integers can only be combined with integers of the same class, or scalar doubles."

[Smruti Khobragade]

Thankyou sir ,

but i wanted the other part other than the desired part to be blackened and then calculate the area.

[Bhaskar R]

That is casting problem, you need to convert both variables to same class. In the answer im>200 gives a logical class to this im mutliplication which is uint8 class not allows the MATLAB thats why uint8 applied to (im>200) explicitly.

[Smruti Khobragade]

i got the output but i wanted the other part other than the desired part to be blackened and then calculate the area.

[Walter Roberson]

res_image = cast(im>200, class(im)).*im;
imshow(res_image)

[Bhaskar R]

These links may help you find area of your image

https://in.mathworks.com/help/images/ref/bwarea.html

https://in.mathworks.com/matlabcentral/answers/318617-how-to-find-the-area

[Smruti Khobragade]

i want to extract some part of original image bsed of pixel values. for example i want to extract part which have pixel values greater than 200 same as the original image not just same color

i mean to say to extract the part of original image based on pixel values the output will be same image with threshold 200 and other blacken.