In a process and unit for gradual decoding, archiving and graphic display of progressively decoded image data, time intervals between the time points of consecutive decoding steps, during which network users receive ever more refined image resolution when downloading image data from a central network server to the client computer using transferred and decoded partial data quantities .DELTA.Li as preview images, are generated with abbreviated time spans that are optimized with respect to minimization of system usage by the decoding system. For this purpose, the receiving data rates for transfer of the individual partial data quantities, which are taken into account through improvements generated by the individual decoding steps of a quality metric showing the degree of image resolution and the temporary usage of the decoding system upon determination of the decoding time points. The wait times between the time points of directly consecutive decoding steps are calculated using statistical image quality parameters of received partial image data in such a manner that the decoding steps which do not lead to a perceptible improvement in the quality of a reconstructed image are suppressed.