v_colormap

PURPOSE ^

V_COLORMAP set and plot color map

SYNOPSIS ^

function [rgb,y,l]=v_colormap(map,m,n,p)

DESCRIPTION ^

V_COLORMAP set and plot color map

   Usage: (1) v_colormap([],'g');          % plot the current color map

          (2) v_colormap([],'',256);       % intepolate the current color map to 256 entries

          (3) v_colormap('copper','y');    % make copper color map linear in luminance

          (4) v_colormap('copper','L');    % make copper color map linear in lightness^2

          (5) imagesc(x);                                  % plot an image containing signed data
              v_colormap('v_bipveey');                     % select a bipolar colormap
              set(gca,'clim',max(abs(x(:)))*[-1 31/32]);   % set the range to make zero=black
              colorbar;                                    % show the color bar

  Inputs:
           map  Either an (r,3) array specifying the RGB colourmap entries
                or else a string specifying a bult-in colour map. Use []
                to leave the colour map unchanged.
                Standard maps are:
                   'Jet','HSV','Hot','Cool','Spring','Summer','Autumn',
                   'Winter','Gray','Bone','Copper','Pink','Lines','Parula'
                Additional maps, all with 64 entries, are:
                   'v_thermliny'  thermal scale that is linear in luminance
                                  Varies from black through blue, red, yellow to white.
                                  Luminance varies linearly from black to white.
                   'v_bipliny'    bipolar scale that is linear in luminance
                                  Negative values are blue/turquoise and postive value are orange/yellow.
                                  Luminance varies linearly from black to white with zero at 50.8% gray.
                   'v_bipveey'    bipolar scale that is V-shaped in luminance
                                  Negative values are blue/turqoise and positive values are red/yellow.
                                  Luminance is proportional to absolute value with zero=black.
                For the two bipolar scales, zero corresponds to entry 33 and so the range of values
                is -32:31 or, equivalently, either -1 to +0.96875 or -1.0323 to +1.

             m  Mode string:
                   'g' to plot information about the color map
                   'y' to force luminance^p to be linear or V-shaped (two linear segments)
                   'l' to force lightness^p to be linear or V-shaped (two linear segments)
                   'Y' like 'y' but with default p=0.667
                   'L' like 'l' but with default p=2
                   'f' flips the map to reverse its order
                   'b' force maximum luminance >=0.05 (or 0.1 for 'B')
                   'w' force maximum luminance <=0.95 (or 0.9 for 'W')
                   'k' to keep the current color map (i.e. don't update it to a new one]

             n  the number of entries in the colourmap or the number in
                each linearly-interpolated segment excluding the entry shared
                with the previous segment. The total number of entries is n=sum(n).
                For modes 'y','Y','l','L' the number of segments must be 1
                or 2; otherwise the number of segments must be 1 or r-1.

             p  power law to use for linearized luminance or lightness [default p=1]
                see the description of 'y' and 'l' for its effect

 Outputs:       Note that the colormap will be updated regardless of whether outputs are
                specified. Use the 'k' option to supress updating.

           rgb  RGB color map entries; one per row.
                All values will be in the range 0 to 1

             y  column vector of luminance values (from CIEXYZ colour space)

             l  column vector of lightness values (lightness is the perceived brightness from CIELUV colour space)

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [rgb,y,l]=v_colormap(map,m,n,p)
0002 %V_COLORMAP set and plot color map
0003 %
0004 %   Usage: (1) v_colormap([],'g');          % plot the current color map
0005 %
0006 %          (2) v_colormap([],'',256);       % intepolate the current color map to 256 entries
0007 %
0008 %          (3) v_colormap('copper','y');    % make copper color map linear in luminance
0009 %
0010 %          (4) v_colormap('copper','L');    % make copper color map linear in lightness^2
0011 %
0012 %          (5) imagesc(x);                                  % plot an image containing signed data
0013 %              v_colormap('v_bipveey');                     % select a bipolar colormap
0014 %              set(gca,'clim',max(abs(x(:)))*[-1 31/32]);   % set the range to make zero=black
0015 %              colorbar;                                    % show the color bar
0016 %
0017 %  Inputs:
0018 %           map  Either an (r,3) array specifying the RGB colourmap entries
0019 %                or else a string specifying a bult-in colour map. Use []
0020 %                to leave the colour map unchanged.
0021 %                Standard maps are:
0022 %                   'Jet','HSV','Hot','Cool','Spring','Summer','Autumn',
0023 %                   'Winter','Gray','Bone','Copper','Pink','Lines','Parula'
0024 %                Additional maps, all with 64 entries, are:
0025 %                   'v_thermliny'  thermal scale that is linear in luminance
0026 %                                  Varies from black through blue, red, yellow to white.
0027 %                                  Luminance varies linearly from black to white.
0028 %                   'v_bipliny'    bipolar scale that is linear in luminance
0029 %                                  Negative values are blue/turquoise and postive value are orange/yellow.
0030 %                                  Luminance varies linearly from black to white with zero at 50.8% gray.
0031 %                   'v_bipveey'    bipolar scale that is V-shaped in luminance
0032 %                                  Negative values are blue/turqoise and positive values are red/yellow.
0033 %                                  Luminance is proportional to absolute value with zero=black.
0034 %                For the two bipolar scales, zero corresponds to entry 33 and so the range of values
0035 %                is -32:31 or, equivalently, either -1 to +0.96875 or -1.0323 to +1.
0036 %
0037 %             m  Mode string:
0038 %                   'g' to plot information about the color map
0039 %                   'y' to force luminance^p to be linear or V-shaped (two linear segments)
0040 %                   'l' to force lightness^p to be linear or V-shaped (two linear segments)
0041 %                   'Y' like 'y' but with default p=0.667
0042 %                   'L' like 'l' but with default p=2
0043 %                   'f' flips the map to reverse its order
0044 %                   'b' force maximum luminance >=0.05 (or 0.1 for 'B')
0045 %                   'w' force maximum luminance <=0.95 (or 0.9 for 'W')
0046 %                   'k' to keep the current color map (i.e. don't update it to a new one]
0047 %
0048 %             n  the number of entries in the colourmap or the number in
0049 %                each linearly-interpolated segment excluding the entry shared
0050 %                with the previous segment. The total number of entries is n=sum(n).
0051 %                For modes 'y','Y','l','L' the number of segments must be 1
0052 %                or 2; otherwise the number of segments must be 1 or r-1.
0053 %
0054 %             p  power law to use for linearized luminance or lightness [default p=1]
0055 %                see the description of 'y' and 'l' for its effect
0056 %
0057 % Outputs:       Note that the colormap will be updated regardless of whether outputs are
0058 %                specified. Use the 'k' option to supress updating.
0059 %
0060 %           rgb  RGB color map entries; one per row.
0061 %                All values will be in the range 0 to 1
0062 %
0063 %             y  column vector of luminance values (from CIEXYZ colour space)
0064 %
0065 %             l  column vector of lightness values (lightness is the perceived brightness from CIELUV colour space)
0066 
0067 % Bugs/Suggestions:
0068 % (1) add option to exclude black from the colormap
0069 
0070 %      Copyright (C) Mike Brookes 2012-2018
0071 %      Version: $Id: v_colormap.m 10866 2018-09-21 17:32:44Z dmb $
0072 %
0073 %   VOICEBOX is a MATLAB toolbox for speech processing.
0074 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
0075 %
0076 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0077 %   This program is free software; you can redistribute it and/or modify
0078 %   it under the terms of the GNU General Public License as published by
0079 %   the Free Software Foundation; either version 2 of the License, or
0080 %   (at your option) any later version.
0081 %
0082 %   This program is distributed in the hope that it will be useful,
0083 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
0084 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0085 %   GNU General Public License for more details.
0086 %
0087 %   You can obtain a copy of the GNU General Public License from
0088 %   http://www.gnu.org/copyleft/gpl.html or by writing to
0089 %   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
0090 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0091 persistent maps nams mcal modes nszs pows la lb lc lci laci lk lq yv
0092 if isempty(maps)
0093     lk=(6/29)^3;
0094     la=841/108;
0095     lb=4/29;
0096     lc=1.16;
0097     lq=la*lc*lk;
0098     lci=1/lc;
0099     laci=lci/la;
0100     %     yv=inv([1.0 0.956 0.621; 1.0 -0.272 -0.647; 1.0 -1.106 1.703]);
0101     %     yv=yv(:,1);
0102     yv=[0.2126; 0.7152; 0.0722];
0103     nams={'v_thermliny','v_bipliny','v_bipveey'};
0104     % modified thermal with better grayscale linearity
0105     mcal=[1 1 1]; % +1 if need to calculate maps entry
0106     modes={'y' 'y' 'y'}; % modes for map calculation
0107     nszs={64 64 [33 31]};  % sizes for maps
0108     pows=[1 1 1];  % powers for maps
0109     maps{1}=[0 0 0; 72 0 167; 252 83 16; 255 249 0; 255 255 255]/255;
0110     % bipolar map with grayscale linearity
0111     maps{2}=[0 0 0; 0 2 203; 1 101 226; 128 128 128; 252 153 12; 252 245 0; 252 249 18; 252 252 252]/252;
0112     maps{3}=[0 0.95 1; 0 0 0.9; 0 0 0; 0.5 0 0; 0.80 0.78 0];
0113 end
0114 if nargin<2
0115     m='';
0116 end
0117 if nargin<4
0118     if any(m=='Y')
0119         p=2/3;
0120     elseif any(m=='L')
0121         p=2;
0122     else
0123         p=1;  % power to raise lightness/luminance to
0124     end
0125 end
0126 pr=1/p;
0127 um=m;
0128 m=lower(m);   % convert mode letters to lower case
0129 oldmap=colormap; % get existing map
0130 rest=0; % do not restore old map by default
0131 if nargin==0 || numel(map)==0     % use existing map
0132     rgb=oldmap;
0133 elseif ischar(map)               % if map given as a string
0134     ix=find(strcmpi(map,nams),1);       % check if it is one of ours
0135     if numel(ix)                        % if it is one of ours
0136         if mcal(ix)             % need to calculate the map the first time around
0137             maps{ix}=v_colormap(maps{ix},modes{ix},nszs{ix},pows(ix));
0138             mcal(ix)=0;                 % don't calculate it again
0139         end
0140         rgb=maps{ix};
0141     else
0142         rgb=colormap(map); % not one of ours - just pass it on to standard colormap function
0143         rest=any(m=='k'); % need to restore the old map if 'k' option is set
0144     end
0145 else
0146     rgb=map; % numeric map specified
0147 end
0148 if any(m=='y') ||  any(m=='l') || (nargin>2 && numel(n)>0) % need to do linear interpolation
0149     nm=size(rgb,1);
0150     if any(m=='y') ||  any(m=='l')
0151         y=rgb*yv;  % convert map to luminance
0152         up=y(2:nm)>y(1:nm-1); % find increasing
0153         ex=up(1:nm-2)~=up(2:nm-1); % +1 for a peak or valley
0154         yd=2*up(1)-1; % +1 if y initially increasing
0155         switch sum(ex)
0156             case 0 % monotonic
0157                 if nargin<3
0158                     r=nm;
0159                 else
0160                     r=n(1);
0161                 end
0162                 if any(m=='y')
0163                     l=y([1 nm]).^p;
0164                     tt=(l(1)+(0:r-1)'*(l(2)-l(1))/(r-1)).^pr; % target luminances
0165                 else
0166                     tt=y([1 nm]');
0167                     l=(lc*(la*tt+(tt>lk).*(tt.^(1/3)-la*tt-lb))).^p;
0168                     tt=(l(1)+(0:r-1)'*(l(2)-l(1))/(r-1)).^pr; % target lightnesses
0169                     tt=laci*tt+(tt>lq).*((lci*tt+lb).^3-laci*tt); % target luminances
0170                 end
0171                 [ss,ix]=sort([tt;y]*yd);
0172             case 1 % V-shaped
0173                 ipk=find(ex,1)+1;  % position of peak/valley in y
0174                 if nargin<3
0175                     n=[ipk nm-ipk];  % size of linear segments
0176                 end
0177                 r=n(1)+n(2);  % total size of map
0178                 if any(m=='y')
0179                     l=y([1 ipk nm]).^p;
0180                     tt=(l(2)+[(1-n(1):0)*(l(2)-l(1))/(n(1)-1) (1:n(2))*(l(3)-l(2))/(n(2))]').^pr; % target luminances
0181                 else
0182                     tt=y([1 ipk nm]');
0183                     l=(lc*(la*tt+(tt>lk).*(tt.^(1/3)-la*tt-lb))).^p;
0184                     tt=(l(2)+[(1-n(1):0)*(l(2)-l(1))/(n(1)-1) (1:n(2))*(l(3)-l(2))/(n(2))]').^pr; % target lightnesses
0185                     tt=laci*tt+(tt>lq).*((lci*tt+lb).^3-laci*tt); % target luminances
0186                 end
0187                 [ss,ix]=sort([tt(1:n(1))-y(ipk); y(ipk)-tt(n(1)+1:r);y(1:ipk)-y(ipk); y(ipk)-y(ipk+1:nm)]*yd);
0188             otherwise
0189                 error('luminance has more than two monotonic segments');
0190         end
0191     else                % just linearly interpolate the given values
0192         if numel(n)==nm-1
0193             r=sum(n);
0194             y=[1;cumsum(n(:))];
0195         else
0196             r=n(1);
0197             y=1+(0:nm-1)'*(r-1)/(nm-1);
0198         end
0199         tt=(1:r)';
0200         [ss,ix]=sort([tt;y]);
0201     end
0202     jx=zeros(size(ix));
0203     jx(ix)=1:numel(jx);
0204     jx=min(max(jx(1:r)-(1:r)',1),nm-1);
0205     al=(tt-y(jx))./(y(jx+1)-y(jx)); % fraction of upper sample to include
0206     rgb=rgb(jx,:)+(rgb(jx+1,:)-rgb(jx,:)).*al(:,ones(1,3)); % update the map
0207 end
0208 if any(m=='f')
0209     rgb=rgb(end:-1:1,:);
0210 end
0211 y=rgb*yv;  % convert RGB to luminance
0212 if any(m=='b') || any(m=='w') % need to constrain luminance
0213     minyt=0.05*(any(m=='b')+any(um=='B')); % target minimum luminance
0214     maxyt=1-0.05*(any(m=='w')+any(um=='W')); % target maximum luminance
0215     maxy=max(y);
0216     miny=min(y);
0217     if maxy>maxyt || miny<minyt
0218         maxy=max(maxy,maxyt);
0219         miny=min(miny,minyt);
0220         rgb=(rgb-miny)*(maxyt-minyt)/(maxy-miny)+minyt;
0221         y=rgb*yv;  % convert RGB to luminance
0222     end
0223 end
0224 l=lc*(la*y+(y>lk).*(y.^(1/3)-la*y-lb)); % convert luminance to lightness
0225 if rest
0226     colormap(oldmap);  % restore the old map
0227 elseif ~isequal(rgb,oldmap)
0228     colormap(rgb); % update the system map
0229 end
0230 if any(m=='g')
0231     sp=[1 2 2];
0232     ssp=sum(sp);
0233     axw=0.05;
0234     nc=size(rgb,1);  % size of color map
0235     hsv=rgb2hsv(rgb);
0236     subplot(ssp,1,sp(1)+(1:sp(2)));
0237     plot(1:nc,y,'--k');
0238     hold on
0239     plot(1:nc,rgb(:,1),'-r');
0240     plot(1:nc,rgb(:,2),'-g');
0241     plot(1:nc,rgb(:,3),'-b');
0242     hold off
0243     axis([0.5 nc+0.5 -axw 1+axw]);
0244     ylabel('RGB + Y');
0245     subplot(ssp,1,sp(1)+sp(2)+1:ssp);
0246     plot(1:nc,l,'--k');
0247     hold on
0248     plot(1:nc,hsv(:,1),'-r');
0249     plot(1:nc,hsv(:,2),'-g');
0250     plot(1:nc,hsv(:,3),'-b');
0251     hold off
0252     axis([0.5 nc+0.5 -axw 1+axw]);
0253     ylabel('HSV + L*');
0254     subplot(ssp,1,1:sp(1));
0255     image(permute(reshape([rgb y(:,[1 1 1])],[nc,3,2]),[3 1 2]));
0256     set(gca,'YTick',[]);
0257 end

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