what does this means.

can you tell me what does this means. .

repmat(okpxls, [1, 1, 3]);

and zeros(size(img), class(img));

pls reply asap. .

Answer 1

[Wayne King]

Enter

size(okpxls)

after the line:

okpxls = minr <= r & r <= maxr & ming <= g & g <= maxg & minb <= b & b <= maxb;

What I think you will see is that okpxls is a 2-D matrix the same size as r, g, and b.

Then the line:

okpxls = repmat(okpxls,[1 1 3])

says take that 2-D matrix okpxls and replicate that exact 2-D matrix into a MxNx3 matrix

Look at this very simple example

x = randn(2,2);
x1 = repmat(x,[1 1 3]);

Now if you enter

size(x1)

You see that x1 is 2x2x3 and furthermore that

x1(:,:,1) is equal to x, x1(:,:,2) is equal to x, and x1(:,:,3) is equal to x

Please read the documentation for repmat.

Answer 2

[Wayne King]

repmat(okpxls,[1 1 3]) replicates (copies) an input into 3-D.

 x = randn(3,1); 
 y = repmat(x,[1 1 3]);

y has the same row and column size as x, but has dimension 3 along the third dimension.

Another example:

   x = randn(2,2);
   y = repmat(x,[1 1 3]);
   size(y) 
zeros(size(img), class(img));

creates a matrix of zeros the same size and class as image

x1 = uint8(randn(8,8)); 
x2 = zeros(size(x1),class(x1));

[Prasad MV]

didn't get clearly though. . .

pls one more try. .

[Wayne King]

if x is 2x2, then y = repmat(x,[1 1 2]) takes that 2x2 matrix and copies that matrix into 2x2x3 matrix where every 3rd dimension is just a copy of the original 2x2 matrix

x = randn(2,2);

y = repmat(x,[1 1 3]);

y is now 2x2x3 and

y(:,:,1)

y(:,:,2)

y(:,:,3)

are all equal to x

[Wayne King]

as far as zeros()

if x has a certain class, say unsigned 8-bit integer

x = uint8(randn(2,2))

size(x)

class(x)

then

y = zeros(size(x),class(x))

creates an array, vector, etc the same size as x AND of the same class

[Prasad MV]

okpxls = minr <= r & r <= maxr & ming <= g & g <= maxg & minb <= b & b <= maxb;

okpxls = repmat(okpxls, [1, 1, 3]);

newimg = zeros(size(img), class(img));

what i didnt get was [1 1 3]

what does this mean