%
% hl_map = hl_color_cycle( bh, bl, br, rh, rl, rg, gh, gl, gb )
%
%	Generates a cyclic color map that is formed of piecewise linear color 
%   ramps between n*pi/6 points, in [B, M, R, Y, G, C] order.
%   
%   USAGE:
%
%       Similar to MATLAB's 'hsv':
%       hl_map = hl_color_cycle( 1,  0,  1,  1,  0,  1,  1, 0,  1 );
%
%       Similar to MATLAB's 'jet':
%       hl_map = hl_color_cycle( 1,  0, .5,  1,  0, .5,  1, 0, .5 );
%       
%       % For a map closer to constant luminance than MATLAB's "hsv", 
%       % use hv.m:
%       hl_map = hl_color_cycle( 1, .4, .95, .95, .35, .8, .85, .3, .8 );
%
%   ARGUMENTS:
%
%       bh, bl      [0,1] Blue high, low values 
%       br          [0,1] Blue-red midpoint value  
%       rh, rl      ...   Red
%       rg 
%       gh, gl      ...   Green
%       gr
%
%   RETURN VALUES:
%
%       hl_map:    256 x 3 matrix containing RGB triplets.
%   
%       Use like:
%
%           colormap( hl_map ),
%
%       or use normalized [0,255] grayscale values as indices into map.
%       See phase2hue_cycle.m for an example.
%
%   HARDCODED:  (see below 'function' statement)
%
%       bShow:  Show color cycle, plot values and approximate luminance.
%
%   CALLS:  (none)
%
%       Called by hl.m
%
%
% Mark Dow,     May 11, 2008
%


function hl_map = hl_color_cycle( bh, bl, br, rh, rl, rg, gh, gl, gb )

%%%%%%%%%%%%%%%%%%%%%%%%
% Hardcoded information:

    bShow = false;  % Show color cycle, plot values 
                    % and approximate luminance.
%
%%%%%%%%%%%%%%%%%%%%%%%%

    hl_map = zeros( 256, 3 );

    for ic = 1:43

        hl_map( ic, 3 ) = bh - (bh-br)*((ic-1)/(43-1));
        hl_map( ic, 1 ) = bl + (br-bl)*((ic-1)/(43-1));

        if bl - (gb-bl)*((ic-0)/(43-1)) > 0
            hl_map( ic, 2 ) = bl - (gb-bl)*((ic-0)/(43-1));
        end
    end
    for ic = 44:86

        hl_map( ic, 1 ) = br + (rh-br)*((ic-43)/(86-43));
        hl_map( ic, 3 ) = br - (br-rl)*((ic-43)/(86-43));

        if rl - (rg-rl)*((87-ic)/(86-44)) > 0
            hl_map( ic, 2 ) = rl - (rg-rl)*((87-ic)/(86-44));
        end
    end
    for ic = 87:128

        hl_map( ic, 1 ) = rh - (rh-rg)*((ic-87)/(128-87));
        hl_map( ic, 2 ) = rl + (rg-rl)*((ic-87)/(128-87));

        if rl - (br-rl)*((ic-86)/(128-87)) > 0
            hl_map( ic, 3 ) = rl - (br-rl)*((ic-86)/(128-87));
        end
    end
    for ic = 129:171

        hl_map( ic, 2 ) = rg + (gh-rg)*((ic-128)/(171-128));
        hl_map( ic, 1 ) = rg - (rg-gl)*((ic-128)/(171-128));

        if gl - (gb-gl)*((172-ic)/(171-130)) > 0
            hl_map( ic, 3 ) = gl - (gb-gl)*((172-ic)/(171-130));
        end
    end
    for ic = 172:214

        hl_map( ic, 2 ) = gh - (gh-gb)*((ic-172)/(214-172));
        hl_map( ic, 3 ) = gl + (gb-gl)*((ic-172)/(214-172));

        if gl - (rg-gl)*((ic-171)/(214-172)) > 0
            hl_map( ic, 1 ) = gl - (rg-gl)*((ic-171)/(214-172));
        end
    end
    for ic = 215:256

        hl_map( ic, 3 ) = gb + (bh-gb)*((ic-214)/(256-214));
        hl_map( ic, 2 ) = gb - (gb-bl)*((ic-214)/(256-214));

        if bl - (br-bl)*((257-ic)/(256-215)) > 0
            hl_map( ic, 1 ) = bl - (br-bl)*((257-ic)/(256-215));
        end
    end

    if bShow 

        figure;
        rgbplot( hl_map )

        imClrBands = repmat( 1:256, 256, 1 );
        figure;
        imshow( imClrBands, hl_map )

        luminance = .3*hl_map(:,1) + .59*hl_map(:,2) + .11*hl_map(:,3);
        figure;
        plot( luminance );
    end