Jan 1, 1971
A method of using a computer-driven graphical plotter to transform a black-and-white photograph from shades of gray to shades of color corresponding to the relative intensity. The human eye can distinguish thousands of colors, but only about 15 shades of gray. This method of enhancing visibility is applied to the JPL Mariner IV photographic system test tapes of a relief map. The digital output of the camera system consists of 200 lines of 200 elements each. Each element is coded with two octal digits representing its intensity, from 0 (lightest) to 63 (darkest). By use of the IBM 7044 with Stromberg-Carlson 4020, the tape data are converted to 64 black-and-white frames, one of each intensity level. The 64 frames are then copied onto a single frame of color film, using a different color filter for each, from red for 0 through orange, yellow, green, and blue for 63. The resulting pseudocolor photograph appears on the cover of the April 1967 [Astronautics and Aeronautics]. The internally documented FORTRAN programs and control cards used are appended.