HI to all.. this is about thresholding the image ..

i am doing with thresholding a image ,i have an image .. for examble

256*256 = 65536 co efficients .. out of that i want to select

65536/4 =16384

with largest absolute values ..

please some body help

[vishnu]

please i nedd help for this

Answer 1

[Chandra Kurniawan]

Hi,

I have small example for 4x4 matrix.

I = round(10*rand(4,4))
J = zeros(size(I,1), size(I,2));

coeff = numel(I)/4;
[B IX] = sort(I(:),'descend');

J(IX(1:coeff)) = 1

The idea is sort the matrix and then select 4 largest element.

See the result below :

I =

       7     8     3     7
       1     7     7     5
       7     9     2     5
       5     9     0     9

J =

       0     1     0     0
       0     0     0     0
       0     1     0     0
       0     1     0     1

To apply this to image, just use the same way :

I = imread('cameraman.tif');
J = zeros(size(I,1), size(I,2));

coeff = numel(I)/4;
[B IX] = sort(I(:),'descend');

J(IX(1:coeff)) = 255;
imshow(uint8(J));

But, I think it takes a long time

[vishnu]

how to verify the number of coefficients or pixels in the image sir..

[vishnu]

thank you for this help

[Chandra Kurniawan]

to verify just

length(find(J));

[vishnu]

thank you