R/T display compression preserving intensity information

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.