Patent No. 4169285 Method for producing color representations of quantifiable data by maximizing differential perception of colors
Patent No. 4169285
Method for producing color representations of quantifiable data by maximizing differential perception of colors (Walker, Sep 25, 1979)
Abstract
A method is described wherein quantifiable data which have arbitrary dynamic ranges and which vary as a function of other parameters are represented in color. A set of subranges, without restriction in number, representing data properties are associated with a color set in such a way that the colors are perceived to be maximally differentiable by interpreters, whether human, electronic, or other, by specifically incorporating information concerning the normal or anomalous characteristics of the interpreter's color perception when determing the color set. The method further provides for the realization of color displays by directly associating the colors with densities, transmittances, or illumination levels for negatives, positives, or colored light emitting devices, whether the realization requires primary additive or primary subtractive hues.
Notes:
BACKGROUND
OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the color display of time series
or space series information which may be discretely sampled or continuous in
nature, in one or more dimensions, or in combination. More particularly, the
present invention relates to a method of producing color displays of information
wherein maximum differential perception by the interpreter of the display is
assured.
2. Description of the Prior Art
Patents have been granted to methods which convert time or space series information
whether called signals, waveforms, functions, graphs, or pictures into color
outputs, the colors of which were assigned on the basis of some property of
the series in question. One such patent, U.S. Pat. No. 3,961,306, teaches a
method wherein the information is scaled into incremental ranges and each range
is assigned a color corresponding to a sample value. The colors are assigned
from a table that is constructed beforehand and which contains information relating
to the densities of the various component displays required to make the assigned
colors. The table is constructed by arbitrarily picking colors.
A shortcoming of the prior art is that the colors must be chosen beforehand,
analyzed, and component densities chosen in order to create an assignment table.
This task becomes arduous for a large number of ranges.
Another shortcoming of the prior art is that there is no teaching in any of
the prior art patents of a method that assures maximal differential perception
of the colors assigned to the output. For example, the usual system for assigning
colors is spectrally; where, for example, large sample values are assigned colors
near the violet end and small sample values are assigned colors near the red
end, with intermediate values assigned in between. When a large number of sample
values are displayed, the differences between colors assigned to closely spaced
values become quite subtle and difficult, if not impossible, to discriminate.
A further shortcoming of the prior art is that there is no teaching of a method
that takes into account color visual deficiencies among observers. There are
color visual anomalies wherein the ability of an individual to perceive certain
hues is either diminished or nonexistent. In methods based on arbitrary assignments
of colors, certain hues that are clearly distinquished by normally sighted individuals
are completely indistinquishable to those with a color vision deficiency. Such
indistinquishability introduces ambiguity into the color display.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for making
color displays that assures maximal differential perception of the colors assigned
to the output. It is a further object of the present invention to provide a
method that provides for maximal differential perception in the case of human
visual or electro-mechanical sensitometric irregularities or deficiencies. It
is a still further object of the present invention to provide a method for flexibly
and directly determining the maximally different colors in terms of primary
additive or primary subtractive hues without the need of first preassigning
values of density, transmittance, or illumination level to numeric codes through
the use of tables or matrices.
Briefly stated, the foregoing and other objectives are accomplished in the present
invention by assigning each measure of the information to be displayed to a
point in a color space such that the distribution density of such points is
substantially equal in certain specified ways. A color display dynamic range
is defined, which comprises an arbitrary number of subranges wherein each subrange
is associated with a distinct color. Each measure of the information to be displayed
is associated with a subrange and, by means of a color contrast parameter, each
subrange is associated with a point in a color space such that the distribution
density of such points is substantially equal.
The present invention further provides a method whereby the spherical coordinates
of each point in the color space may be transformed into Cartesian coordinates,
which may be directly converted into densities, transmittances or illumination
levels, of primary hues necessary to produce the display. The present invention
also provides a method by which color visual deficiencies of the interpreter
may be compensated for.
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