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 “Pepper” 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 at least two different blocks sizes, e.g., 8x8 and 16x16. Devise a scheme to reduce
the blocked data in the DCT domain using an energy-based or another ‘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 using performance measures such as distortion or signal-tonoise ratio (use 10log ( ) 2
2
10
e
o SNRdB σ
σ = where 2 σ o is the variance of the original image
and 2 σ e is the variance of the error image) as well as visual evaluation of the results.
2. DWT Approach: Apply 2-D DWT to the same image and display the results for two and
three-level decompositions and two different choices of wavelets e.g., Daubechies (db),
Symlet (sym),), etc. Present the histograms of the sub-images and compare the data reduction
ability of the two transforms in Parts 1 and 2. Compare the best results of the DWT with that
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.
