Presentation on theme: "A COMPARATIVE STUDY OF DCT AND WAVELET-BASED IMAGE CODING & RECONSTRUCTION Mr. S Majumder & Dr. Md. A Hussain Department of Electronics & Communication."— Presentation transcript:
A COMPARATIVE STUDY OF DCT AND WAVELET-BASED IMAGE CODING & RECONSTRUCTION Mr. S Majumder & Dr. Md. A Hussain Department of Electronics & Communication Engineering NERIST (North Eastern Regional Institute of Science & Technology) (Deemed University), Arunachal Pradesh firstname.lastname@example.org & email@example.com
IMAGE COMPRESSION THE NEED FOR COMPRESSION 1.Spatial redundancy Correlation between neighboring pixels values 2. Spectral redundancy Correlation between different spectral bands INTRODUCTION TO IMAGE COMPRESSION 1.Lossless compression 2.Lossy compression OBJECTIVE 1.Minimum distortion 2.High compression ratio 3.Fast computation time
DCT-Based Image Coding Standard The DCT can be regarded as a discrete-time version of the Fourier-Cosine series. It is a close relative of DFT, a technique for converting a signal into elementary frequency components. Thus DCT can be computed with a Fast Fourier Transform (FFT) like algorithm in O(n log n) operations. Unlike DFT, DCT is real-valued and provides a better approximation of a signal with fewer coefficients. The DCT of a discrete signal x(n), n=0, 1,.., N-1 is defined as: where, C(u) = 0.707 for u = 0 and = 1 otherwise.
ENTROPY ENCODING The quantized data contains redundant information. It is a waste of storage space if we were to save the redundancies of the quantized data. Run-Length Encoding Huffman Encoding ENTROPY ENCODING
CONCLUSION For still images, the wavelet transform based compression outperforms the DCT based compression typically in terms of the compressed output for different quantization levels, as well as the reconstructed image quality. For the same reconstructed image size of 14 Kb and equivalent image clarity, DWT based coded image requires less than half transmission bandwidth and storage requirement as compared to DCT based coded image.
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