METHOD AND APPARATUS FOR CREATING LESS AMOUNT OF COMPRESSED IMAGE DATA FROM COMPRESSED STILL IMAGE DATA AND SYSTEM FOR TRANSMITTING COMPRESSED IMAGE DATA THROUGH TRANSMISSION LINE

Compressed image data of a desired picture is read out from a memory having compressed image data of a sequential format stored therein and then subjected to an examination with respect to a plurality of frequency components of the read-out compressed image data. Part of the plurality of frequency components is deleted to obtain compressed image data of a quality lower than an original quality of the compressed image data. The obtained compressed image data of the lower quality is decoded and displayed on a display. The plurality of frequency components are deleted in a stepwise manner according to a traffic state of a transmission line through which the compressed image data is to be transmitted. For maintaining a picture frame rate to be constant, the plurality of frequency components may be deleted in a stepwise manner. For obtaining a desired decoding rate, the plurality of frequency components may be deleted in a stepwise manner.