A. Ramaswamy et Wb. Mikhael, COMPRESSION OF IMAGES REPRESENTED USING MULTI-TRANSFORMS, Journal of circuits, systems, and computers, 6(1), 1996, pp. 41-57
Constrained image representation employing multi-transforms has been r
ecently developed. First, the image is divided into smaller non-overla
pping subimages. Each subimage is resolved appropriately into 2-D subs
ignals, each of which is compactly represented in a specific transform
domain. The subimage is efficiently represented by superimposing the
dominant components corresponding to the subsignals. The residual erro
r, which is the difference between the original subimage and the recon
structed subimage is minimized by adaptive algorithms. An optimization
strategy selects the dominant coefficients from the various domains f
or adaptation. An efficient coding technique is presented to code the
multi-transform coefficients. An image representation example is prese
nted employing the DCT-Haar combination. Objective evaluations are mad
e where it is shown that images represented using the multi-transform
technique are more accurate than using the DCT for the same number of
retained transform coefficients. Test subimages with a high amount of
detail represented using the proposed technique show an SNR improvemen
t of about 3 to 4 dB over using DCT alone. Finally, images, coded at b
it rates of 0.44 bits/pixel and 1.23 bits/pixel employing the proposed
technique verify the good quality of reconstruction.