jpeg image compression

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nasim alam
nasim alam 2011-3-9
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 "

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回答（2 个）

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')
Walter Roberson
Walter Roberson 2011-3-9
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.
  2 个评论
Sarah Wait Zaranek
Sarah Wait Zaranek 2011-3-9
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
Walter Roberson 2011-3-9
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.

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