808 |
Color is the most dominant visual attribute of a texture. |
Color is the most dominant visual attribute of a texture. |
809 |
Therefore, it is essential that the overall colors of the |
Therefore, it is essential that the overall colors of the |
810 |
backgrounds are maximally diverse with respect to color perception. |
backgrounds are maximally diverse with respect to color perception. |
811 |
However, we come again to the entropy arguments |
However, we come again to the number-of-different-features arguments |
812 |
of Section~\ref{secfeaturevec}: |
of Section~\ref{secfeaturevec}: |
813 |
too many different colors in one background are perceived just |
too many different colors in a {\em single} background are perceived just |
814 |
as a mix of many colors, making all such backgrounds look the same. |
as a mix of many colors, making all such backgrounds look the same. |
815 |
|
|
816 |
To maintain color balance, |
To maintain recognizability, |
817 |
we use a heuristically selected |
we use a |
818 |
small palette of colors for each paper. |
small palette of colors for each paper, selected |
819 |
|
randomly from a heuristic distribution. |
820 |
The final image contains convex combinations of |
The final image contains convex combinations of |
821 |
the palette colors. |
the palette colors. |
822 |
|
|
825 |
random colors (cf. \cite{healey96choosing}): |
random colors (cf. \cite{healey96choosing}): |
826 |
using a uniformly chosen hue angle |
using a uniformly chosen hue angle |
827 |
produces too much blue and too little yellow |
produces too much blue and too little yellow |
828 |
for high $L^*$. |
for high $L^*$ (luminance). |
829 |
Because of this, we use a different color circle |
Because of this, we use a different color circle |
830 |
with seven evenly spaced ``primary'' hues (RGB, CMY and orange). |
with seven evenly spaced ``primary'' hues (RGB, CMY and orange). |
831 |
% |
% |
880 |
palette because the adaptive effects of the eye shift them |
palette because the adaptive effects of the eye shift them |
881 |
towards the complementary colors of the more saturated colors |
towards the complementary colors of the more saturated colors |
882 |
in the palette. |
in the palette. |
883 |
|
|
884 |
% |
% |
885 |
%Usually, only a maximum circle |
%Usually, only a maximum circle |
886 |
%contained in the gamut of a given lightness level is used for |
%contained in the gamut of a given lightness level is used for |
915 |
%Note that for correct computation of the lightness, |
%Note that for correct computation of the lightness, |
916 |
%it is essential that the display gamma is properly adjusted |
%it is essential that the display gamma is properly adjusted |
917 |
%for linear (XXX: usually around gamma 2) RGB reproduction. |
%for linear (XXX: usually around gamma 2) RGB reproduction. |
|
|
|
918 |
For each background, |
For each background, |
919 |
we use colors from {\em both} the dark and light end of the |
we use colors from {\em both} the dark and light end of the |
920 |
80-100 range in order to create some contrast. |
80-100 range in order to create some contrast. |