09-11-2012, 05:09 PM
Implementation Of Image Compression Using DCT Abstract
The DCT is a loss-less and reversible mathematical transformation that converts a spatial amplitude representation of data into a spatial frequency representation. The DCT has been used in many applications such as filtering, transmultiplexers, speech coding, image coding (still frame, video and image storage), pattern recognition, image enhancement, and SAR/IR image coding. The DCT is widely used in image compression applications, especially in lossy image compression. For example, the 2D DCT is used for JPEG still image compression, MPEG moving image compression, and the H.261 and H.263 video-telephony coding schemes. The energy compaction property of the DCT is well suited for image compression since, as in most images, the energy is concentrated in the low to middle frequencies, and the human eye is more sensitive to the middle frequencies. On the other hand, the Fast Fourier Transform (FFT) is easy to implement, but does not provide an adequate compression ratio.
In this project we implement a lossy image and sound compressions technique where thediscret cosine transform of the signal is performed, then calculated a threshold based on the compression ratio required by the user. The compression is done by using the Matlab toolbox and Matlab functions.