jens
b31f3e7435
git-svn-id: http://moon:8086/svn/matlab/trunk@153 801c6759-fa7c-4059-a304-17956f83a07c
48 lines
1.3 KiB
Matlab
Executable File
48 lines
1.3 KiB
Matlab
Executable File
% function [lab] = xyz2cielab(xyz, ref_xyz)
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%
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% // C-Code
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% var_X = X / 95.047 //Observer = 2°, Illuminant = D65
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% var_Y = Y / 100.000
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% var_Z = Z / 108.883
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%
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% if ( var_X > 0.008856 ) var_X = var_X ^ ( 1/3 )
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% else var_X = ( 7.787 * var_X ) + ( 16 / 116 )
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% if ( var_Y > 0.008856 ) var_Y = var_Y ^ ( 1/3 )
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% else var_Y = ( 7.787 * var_Y ) + ( 16 / 116 )
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% if ( var_Z > 0.008856 ) var_Z = var_Z ^ ( 1/3 )
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% else var_Z = ( 7.787 * var_Z ) + ( 16 / 116 )
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%
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% CIE-L* = ( 116 * var_Y ) - 16
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% CIE-a* = 500 * ( var_X - var_Y )
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% CIE-b* = 200 * ( var_Y - var_Z )
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%
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% Source http://www.easyrgb.com
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function [lab] = xyz2cielab(xyz, ref_xyz)
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[m,n] = size(xyz);
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if ((m ~= 3) & (n == 3))
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xyz = xyz'
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end;
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xyz(1,:) = xyz(1,:)./ref_xyz(1,:);
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xyz(2,:) = xyz(2,:)./ref_xyz(2,:);
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xyz(3,:) = xyz(3,:)./ref_xyz(3,:);
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xyz_k = f1(xyz);
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% L
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lab(1,:) = 116*xyz_k(2,:) - 16;
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% a
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lab(2,:) = 500*(xyz_k(1,:) - xyz_k(2,:));
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% b
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lab(3,:) = 200*(xyz_k(2,:) - xyz_k(3,:));
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function xyz_k = f1(xyz)
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thresh_n = 0.008856;
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[idx_m, idx_n] = find(xyz > thresh_n);
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xyz_k(idx_m,idx_n) = xyz(idx_m,idx_n).^(1/3);
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[idx_m, idx_n] = find(xyz <= thresh_n);
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xyz_k(idx_m,idx_n) = 7.787 * xyz(idx_m,idx_n) + 16/116;
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