Multidimensional transform: Difference between revisions

Revision as of 06:46, 12 March 2023

Revision as of 03:21, 11 December 2023

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[[File:Dctjpeg.png|thumb|250px|Two-dimensional DCT frequencies from the [[JPEG#Discrete cosine transform|JPEG DCT]]]]

The DCT is used in [[JPEG]] image compression, [[MJPEG]], [[MPEG]], [[DV (video format)|DV]], [[Daala]], and [[Theora]] [[video compression]]. There, the two-dimensional DCT-II of ''N''x''N'' blocks are computed and the results are [[Quantization (signal processing)|quantized]] and [[Entropy encoding|entropy coded]]. In this case, ''N'' is typically 8 and the DCT-II formula is applied to each row and column of the block. The result is an 8x8 transform coefficient array in which the: (0,0) element (top-left) is the DC (zero-frequency) component and entries with increasing vertical and horizontal index values represent higher vertical and horizontal spatial frequencies, as shown in the picture on the right.

In image processing, one can also analyze and describe unconventional cryptographic methods based on 2D DCTs, for inserting non-visible binary watermarks into the 2D image plane,<ref>Peter KULLAI, Pavol SABAKAI, JozefHUSKAI. Simple Possibilities of 2D DCT Application in Digital