Image Transforms

Digital Image Processing (ECE513) Computer Project 2: Image Transforms For Data Compression The goal of this computer assignment is to study and compare two different image transforms, namely 2-D DCT and DWT, for the purpose of image data compression. The “Lena” image (see course web page under Images) is used for this assignment. 1. DCT Approach: Partition the image into non-overlapping blocks and apply DCT to each block. Use two different blocks sizes, e.g., 8×8 and 16×16. Devise a scheme to reduce the blocked data in the DCT domain using an energy-based or other ‘meaningful’ criterion (e.g., histogram of the DCT coefficients). For each block-size and data reduction criterion, reconstruct the image from the retrained coefficients and display the results. Compare the results of your reconstructions based on visual evaluation of the results and also using signal- σ o2 to-noise ratio, ( SNRdB = 10 log10 ( σ e2 ) where σ o2 is the variance of the original image and σ e2 is the variance of the error image, for different percent reduction. 2. DWT Approach: Apply 2-D DWT to the same image and display the results for two and three-level decompositions using Daubechies (db) wavelets. Present the histograms of the sub-images and compare the data reduction ability of the two transforms in Parts 1 and 2 in terms of SNR vs percent reduction. Note: compare the best results of the DWT with the best result of the DCT for the cases studied. 3. Provide a detailed discussion on the effectiveness of this transform for image data reduction and representation in a report. Please read the guidelines for preparing your report.