Display of Grey-Scale Data on a Bilevel Output Device
, by Steve Cole and Joe Dellinger
Graphics display devices that allow the intensity of each pixel to be varied are ideal for displaying seismic data, since the intensity of each pixel can indicate the amplitude of the corresponding sample of the seismic data set. Hardcopy devices do not allow the intensity of individual pixels to be varied --- each must be ``on'' or ``off''.
It is possible to achieve the effect of intensity variation on such
devices by controlling the spatial density of ``on'' and ``off'' pixels. Each pixel in the continuous-tone image is compared to a threshold value. If the input intensity is greater than the threshold, the corresponding pixel of the output device is set to ``on''. Otherwise it is set to ``off''. The methods available for accomplishing this differ in the way that threshold values are obtained.
We find these techniques capable of generating hardcopy images that are
similar in quality to graphics screen images. For many applications,
these displays are preferable to conventional ``wiggle
trace'' displays of seismic data, which overcome the lack of intensity
variation by using the amplitude of the wiggle trace to represent the
amplitude of the corresponding sample of the seismic data set.
STANFORD