Why is the Fourier (or cosine) transform decorrelating?

1. What is the purpose of discrete cosine transform?
2. What is decorrelation in image processing?
3. What are the advantages of discrete cosine transform?
4. Why use DCT instead of DFT?

What is the purpose of discrete cosine transform?

Definition:Discrete Cosine Transform is a technique applied to image pixels in spatial domain in order to transform them into a frequency domain in which redundancy can be identified.

What is decorrelation in image processing?

Decorrelation stretching enhances the color separation of an image with significant band-to-band correlation. The exaggerated colors improve visual interpretation and make feature discrimination easier. You apply decorrelation stretching with the decorrstretch function.

What are the advantages of discrete cosine transform?

1) The DCT is real-valued instead of complexity (i.e., it involves magnitude and phase) such that it is easier to be implemented. 2) The DCT is more efficient for illumination variation estimation than the DWT. 3) The DCT approach is similar to the homomorphic filtering, which has been used for contrast enhancement.

Why use DCT instead of DFT?

> DCT is preferred over DFT in image compression algorithms like JPEG > because DCT is a real transform which results in a single real number per > data point. In contrast, a DFT results in a complex number (real and > imaginary parts) which requires double the memory for storage.