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revision 1.92 by tjl, Fri Nov 29 09:49:26 2002 UTC revision 1.93 by tjl, Fri Nov 29 09:57:02 2002 UTC
# Line 496  a relatively large texture has to be use Line 496  a relatively large texture has to be use
496  Color is the most dominant visual attribute of a texture.  Color is the most dominant visual attribute of a texture.
497  Therefore, it is essential that the overall colors of the  Therefore, it is essential that the overall colors of the
498  backgrounds are maximally diverse with respect to color perception.  backgrounds are maximally diverse with respect to color perception.
   
499  However, we come again to the entropy arguments  However, we come again to the entropy arguments
500  in Section~\ref{secfeaturevec}:  in Section~\ref{secfeaturevec}:
501  too many different colors in one background are perceived just  too many different colors in one background are perceived just
502  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.
503  The backgrounds of random texels discussed earlier are an  The backgrounds of random texels discussed earlier are an
504  extreme example of this.  extreme example of this.
505    To maintain color balance,
506    we use a small palette of colors for each background,
507    chosen by heuristic perceptual methods.
508    
509  %In addition to choosing perceptually diverse colors,  %In addition to choosing perceptually diverse colors,
510  %there is the the question of how many colors to use.  %there is the the question of how many colors to use.
# Line 510  extreme example of this. Line 512  extreme example of this.
512  % Using multiple different colors in a background allows  % Using multiple different colors in a background allows
513  % a multitude of different combinations  % a multitude of different combinations
514    
 To maintain color balance,  
 we use a small palette  
 of carefully chosen colors for each background,  
   
515  % independent of the basis textures producing  % independent of the basis textures producing
516  % the shapes of the background.  % the shapes of the background.
517  % Register combiners are used to combine the shape with the colors  % Register combiners are used to combine the shape with the colors
# Line 538  color space is reasonably perceptually u Line 536  color space is reasonably perceptually u
536  %  2) not really uniform; it's MORE uniform than RGB but not  %  2) not really uniform; it's MORE uniform than RGB but not
537  %     absolutely uniform  %     absolutely uniform
538    
539  To address readability, we only use colors with the CIE $L^*$  For readability, we only use colors with the CIE $L^*$
540  lightness value over 80 (percent of maximum).  lightness value over 80 (percent of maximum).
541  % Mention screen gamma earlier, maybe here.  Note that for correct computation of the lightness,
 For correct computation of the lightness,  
542  it is essential that the display gamma is properly adjusted  it is essential that the display gamma is properly adjusted
543  for linear RGB reproduction.  for linear RGB reproduction.
 % Onko lineaarinen *varmasti* oikea LAB-muunnokselle?  
544    
545  Because the shapes should also be distinguishable,  For each background,
546  we use one half dark colors and one half light colors in the  we use colors from {\em both} the dark and light end of the
547  range to have some contrast for the shapes.  80-100 range in order to create some contrast.
548  This avoids the unpleasant, blurry appearance of backgrounds with only  This makes the shapes in the texture distinguishable,
549    and avoids the unpleasant, blurry appearance of backgrounds with only
550  chroma changes in colors.  chroma changes in colors.
551  %Having contrast makes shapes distinguishable  %Having contrast makes shapes distinguishable
552    
# Line 560  chroma changes in colors. Line 557  chroma changes in colors.
557  %% Doesn't really need to be said here; it's what people  %% Doesn't really need to be said here; it's what people
558  %% will naturally assume.  %% will naturally assume.
559    
560  To produce compatible colors, we choose the hue angles from a distribution  To produce compatible colors, we choose
561  % To have: huonoa englantia  the hue angles from a distribution
562  concentrated on one random hue with a random variance and  concentrated on one random hue with a random variance and
563  saturations from an ad hoc distribution.  saturations from an ad hoc distribution.
564  This produces related colors with high probability, but still  This produces related colors with high probability, but still
# Line 793  XXX Line 790  XXX
790  \label{fig-identity-via-textures}  \label{fig-identity-via-textures}
791  a) different documents with similar appearance and a focus+context view  a) different documents with similar appearance and a focus+context view
792  showing relations,  showing relations,
793  b) the same documents and the same view with identity visualized with unique backgrounds  b) the same documents and the same view with identity visualized with unique backgrounds. If viewing this document on a screen, make sure the your gamma is properly set; the text {\bf is} readable if the gamma is correct but the textures are too dark if not.
794  }  }
795  \end{figure*}  \end{figure*}
796    

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