My DCT image is showing a zero matrix. Why is it so?

I converted YUV image to gray and then found its DCT and IDCT. The resulting image(IDCT one) is showing a zero matrix when I view it through imread command. I can't understand the reason behind it. And secondly, how to reduce the no. of elements of a matrix? For example say, I want to reduce my matrix form 10*10 to 8*8 one?

Answer 1

[Walter Roberson]

You forgot to uint8() the result of the idct before using imwrite()

[Chandvi Arora]

Can you please provide a demo code to explain this further?

[Walter Roberson]

Suppose that you have named the result of the idct to be Result. Then between the idct and the imwrite add

Result = uint8( Result) ;

After that proceed to imwrite