Why discrete cosine transform may not maintain locality

1. What is the purpose of discrete cosine transform?
2. Is discrete cosine transform lossless?
3. Why is DCT better than DFT?
4. Why is DCT useful in compression?

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.

Is discrete cosine transform lossless?

This allows the DCT technique to be used for lossless compression of images. It is a modification of the original DCT algorithm, and incorporates elements of inverse DCT and delta modulation. It is a more effective lossless compression algorithm than entropy coding.

Why is DCT better than 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.

Why is DCT useful in compression?

The DCT has the property that, for a typical image, most of the visually significant information about the image is concentrated in just a few coefficients of the DCT. For this reason, the DCT is often used in image compression applications.