Pyramid data structures have found an important role in progressive image transmission.
In these data structures, the image is hierarchically represented where each level corresponds to
a reduced-resolution approximation. To achieve progressive image transmission, the pyramid is
transmitted starting from the top level. However, in the usual pyramid data structures, extra
significant bits may be required to accurately record the node values, the number of data to be
transmitted may be expanded and the node values may be highly correlated. In this paper, we
introduce a reduced-difference pyramid data structure where the number of nodes, corresponding
to a set of decorrelated difference values, is exactly equal to the number of pixels. Experimental
results demonstrate that the reduced-difference pyramid results in lossless progressive image
transmission with some degree of compression. By using an appropriate interpolation niethod,
reasonable quality approximations are achieved at a bit rate less than 0.1 bits/pixel and excellent
quality at a bit rate of about 1.2 bits/pixel.