how to get dct co-efficients of a compressed image

Hi all, am a student of M.tech doing a project on image processing in Matlab, my project is doing different operations on compressed image directly. so in order to do tat 1st i want to know "how to get DCT co-efficients of an compressed image"

please help me in finding the same...

Thank you, Raj,

Answer 1

[Wayne King]

Please read the documentation for dct2

>>doc dct2

[Muthuraj V]

Can u please send me the exact download link for the same..

Thank You,

[Walter Roberson]

http://www.mathworks.com/help/toolbox/images/ref/dct2.html

[Muthuraj V]

Thank for the information,

but i wanted to get the DCT coefficients of an image in compressed domain i.e without compressing it.

can u please check with that.

Thank You

[Walter Roberson]

If you have an existing JPEG image and you want to retrieve the stored DCT coefficients, then you will need to study the JPEG file format and write a routine to pull them out of the JPEG file.

You might be able to find an existing routine that could be adapted for your purposes in the MATLAB File Exchange.