jpeg image compression

what is the coding for jpeg image compression using 2-D DCT transform.

what is the meaning of this sentence :- " if ndims(x)~=2 | ~isreal(x) | ~isnumeric(x) | ~isa(x, 'uint8') error ('The input must be a unit8 image.'); end "

Answer 1

[Sarah Wait Zaranek]

This is a logical statement, let's break it down - english on left, MATLAB on right.

if the number of dimensions of x is not equal to 2 (ndims(x)~=2)

or (|)

is not real (~isreal(x))

or (|)

is not numeric (~isnumeric(x))

or (|)

is not an unsigned 8 bit integer ( ~isa(x, 'uint8') )

then throw the error

"The input must be a ....." (error('message here')

Answer 2

[Walter Roberson]

ndims is the number of dimensions of the array. Arrays 3 dimensions (RGB) or larger are rejected.

isreal() tests whether the data contains imaginary components; the code rejects if it does.

isnumeric() tests for cell arrays, strings, logicals symbolic numbers and objects; the code rejects the data if it contains anything but numbers.

is(x,'uint8') tests to see whether the data is unsigned 8 bit numbers; the code rejects the data if it is not.

[Sarah Wait Zaranek]

Walter,

I think we duplicated each others answers here. Probably both submitted at the same. Do you want to merge them?

Cheers,

Sarah

[Walter Roberson]

I'm not sure it's worth the time spent editing, as I do not expect that many people will end up referring to the question unless drawn in by the inexact title.