WEEK 9 FYP 2

Title:
Research for Discrete Cosine Transformation (DCT)

Objective:
To know deeply about Discrete Cosine Transformation (DCT) method used in Image Steganography

Content/Result:

• The DCT transforms a signal or image from the spatial domain to the frequency domain. 

• It separates the image into parts (or spectral sub-bands) of differing importance (with respect to the image's visual quality). 

• It can separate the image into High, Middle and Low Frequency components. 

• The human eye is able to catch modifications to the lower frequencies since most of the image's frequency content is located in this area.  

• For each color component, the JPEG image format uses a discrete cosine transform (DCT) to transform successive 8 × 8 pixel blocks of the image into 64 DCT coefficients each. The DCT coefficients F(u, v) of an 8 × 8 block of image pixels f(x, y) are given by 

DCT 8x8 basic function

             

Original image before DCT applied

Original image after DCT applied

Conclusion:
The JPEG image format uses a discrete cosine transform (DCT) to transform successive 8 × 8 pixel blocks of the image into 64 DCT coefficients each. It can separate the image into High, Middle and Low Frequency components. The human eye is able to catch modifications to the lower frequencies since most of the image's frequency content is located in this area.