a realtime display compression for a waveform image uses a priority basis for combining groups of pixels when producing a compressed waveform image in order to preserve intensity information . as an example successive lines of data for the waveform image are demultiplexed into line buffers in a circulating manner , the number of line buffers being a function of the maximum desired integer compression ratio . the outputs from the line buffers are aligned and the corresponding pixels are combined according to a desired compression ratio , one output line for each integer compression ratio . the appropriate compressed line is selected as the output line according to the desired compression ratio , with the totality of the output lines forming the compressed waveform image .