Block Based DCT on gray images

0
votes

Can IDCT give negative values after applying it to block based DCT channels? I divided the gray image in 4*4 blocks and they took the 4*4 DCT of the blocks. Then using those blocks i created DCT channels. Each channel contained the spread of a frequency over the image.

1
image-processingdct
Please show a Minimum Complete Verifiable Example. Thank you. – Mark Setchell
@MarkSetchell: code is not required, the question is about a mathematical property. In fact the question does not belong here. – Yves Daoust

1 Answers

2
votes

Yes it can. The DCT is a sum of cosines, which have zero mean. So you may very well have nonzero pixels with negative weights only.