## What is discrete cosine transform in image processing?

The discrete cosine transform (DCT) helps separate the image into parts (or spectral sub-bands) of differing importance (with respect to the image’s visual quality). The DCT is similar to the discrete Fourier transform: it transforms a signal or image from the spatial domain to the frequency domain (Fig 7.8).

### What is digital image watermarking?

Digital image watermarking is a technique in which watermark data is embedded into a multimedia product and, later, is extracted from or detected in the watermarked product. These methods ensure tamper-resistance, authentication, content verification, and integration of the image [1].

What is DCT watermarking?

DCT Transform Digital Watermarking is similar to spatial domain watermarking except, instead of altering the image bit plane pixel LSB, the frequency coefficients are alternated. The DCT transform is based on dividing the original image into 8 X 8 blocks of pixels and applying the transform individually to each block.

How does discrete cosine transform work?

A discrete cosine transform (DCT) expresses a finite sequence of data points in terms of a sum of cosine functions oscillating at different frequencies. In particular, a DCT is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers.

## What is DFT used for?

The Discrete Fourier Transform (DFT) is of paramount importance in all areas of digital signal processing. It is used to derive a frequency-domain (spectral) representation of the signal.

### What kind of transforms are used in watermarking?

There are a number of transforms that can be applied to digital images, but there are notably three most commonly used in image watermarking. They are Discrete Fourier Transform (DFT), Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT).

How is a discrete cosine transform related to DFT?

Discrete Cosine Transform is related to DFT in a sense that it transforms a time domain signal into its frequency components. The DCT however only uses the real parts of the DFT coefficients.

How is a watermark added to an image?

The watermark is added in select coefficients with significant image energy in the transform domain in order to ensure non- erasability of the watermark.

## What do you need to know about digital watermarking?

Digital watermarking technology is an emerging field in computer science, cryptography, signal processing and communications. Digital watermarking is intended by its developers as the solution to the need to provide value added protection on top of data encryption and scrambling for content protection.

What is discrete cosine transform in image processing? The discrete cosine transform (DCT) helps separate the image into parts (or spectral sub-bands) of differing importance (with respect to the image’s visual quality). The DCT is similar to the discrete Fourier transform: it transforms a signal or image from the spatial domain to the frequency domain…