CONDITION CHECKING R G B VALUES IN AN IMAGE WITH SCALAR USING MATLAB?

hi, I have an image 'pq'(RGB image), which is shown below

now i want to check the following conditions by obtaining the R, G, B from the image

Where R, G, B are

 R=pq(:,1)
 G=pq(:,2)
 B=pq(:,3)

[Ameer Hamza]

What does the condition

(R>=1 && R<=250) && (G>=0 && G<=1) && (B>=0 && B<=255)

mean. An image does not have just one pixel. The image has several pixels. What does R, G and B represent? Value of just one pixel or average value over the entire image.

[Paolo]

Are you just asking how to extract data from Excel?

 num = xlsread('pq.xlsx')
 R = num(:,1);
 G = num(:,2);
 B = num(:,3);

[meenu v]

 R=pq(:,1)
 G=pq(:,2)
 B=pq(:,3)

[Paolo]

Yes, that's the same thing?

[meenu v]

Yp,but on excecution it is showing the error

 "Operands to the || and && operators must be convertible to logical scalar values."

[Paolo]

The following works for me:

 num = xlsread('pq.xlsx')
 R = num(:,1);
 G = num(:,2);
 B = num(:,3);

 for ii=1:numel(R)
     if(R(ii)>=1 && R(ii)<=250) && (G(ii)>=0 && G(ii)<=1) && (B(ii)>=0 && B(ii)<=255)
         disp(R(ii));
     end
 end

Are you sure that the second condition is correct for the green value? Because you are checking between 0 and 1 only.

Answer 1

[Image Analyst]

Try this:

[rows, columns] = size(pq)
for row = 1 : rows
    R = pq(row, 1);
    G = pq(row, 2);
    B = pq(row, 3);
    if (R>=1 && R<=250) && (G>=0 && G<=1) && (B>=0 && B<=255)
        % and so on....
    end
end

Answer 2

[Ameer Hamza]

You can solve the error by converting && to a single &

(R>=1 & R<=250) & (G>=0 & G<=1) & (B>=0 & B<=255)

but I doubt it will actually do, what you are thinking it will do.

[Paolo]

Yes, I think this is the solution he needs.

[Ameer Hamza]

But OP needs to understand that using a vector logical expression with if and while condition need to be handled carefully. The expression is essentially equaled to

if all((R>=1 & R<=250) & (G>=0 & G<=1) & (B>=0 & B<=255))

Unless the requirement is to apply the same condition to every pixel. This will probably result in a wrong logic.

[Image Analyst]

Yeah we talked about all this in his earlier question - about whether to use single or double ampersands. Now (in this question) he has an array pq, that seems to be a subset of all the pixels in the image. Perhaps from a masking operation - who knows? That's what I do in my answer - just the subset. Regardless, I still have doubts he knows what he wants to do, or is asking the correct question.