| 摘要 |
<p>To prepare digital image data for transmission via channels having a limited transmission capacity, a transformation coding is usually used for obtaining decorrelated coefficients. These coefficients are then quantised and transmitted. At the receiving end, the image is reconstructed from the quantised coefficients. The image content has previously been processed block by block which resulted in block-like interference patterns in coded images. In the invention, no block-by-block processing is used but image segments of any shape, which can be advantageously adapted to the local image content, are subjected to a transformation. For this purpose, a set of linearly independent two-dimensional basic functions is determined, the local extent of which is selected in such a manner as corresponds to a rectangle circumscribing the respective segment. New orthogonal basic functions are obtained by an orthogonalisation applied to the basic functions. For determining the coefficients describing the respective segment, the set of new orthogonal basic functions is applied in accordance with the transformation rule for rectangular areas.</p> |
