jens
b31f3e7435
git-svn-id: http://moon:8086/svn/matlab/trunk@153 801c6759-fa7c-4059-a304-17956f83a07c
46 lines
1.3 KiB
Matlab
Executable File
46 lines
1.3 KiB
Matlab
Executable File
% function [xyz] = cielab2xyz(lab, ref_xyz)
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%
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% // C-Code
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% var_Y = ( CIE-L* + 16 ) / 116
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% var_X = CIE-a* / 500 + var_Y
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% var_Z = var_Y - CIE-b* / 200
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%
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% if ( var_Y^3 > 0.008856 ) var_Y = var_Y^3
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% else var_Y = ( var_Y - 16 / 116 ) / 7.787
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% if ( var_X^3 > 0.008856 ) var_X = var_X^3
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% else var_X = ( var_X - 16 / 116 ) / 7.787
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% if ( var_Z^3 > 0.008856 ) var_Z = var_Z^3
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% else var_Z = ( var_Z - 16 / 116 ) / 7.787
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%
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% X = ref_X * var_X //ref_X = 95.047 Observer= 2°, Illuminant= D65
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% Y = ref_Y * var_Y //ref_Y = 100.000
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% Z = ref_Z * var_Z //ref_Z = 108.883
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%
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% Source http://www.easyrgb.com
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function [xyz] = cielab2xyz(lab, ref_xyz)
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[m,n] = size(lab);
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if ((m ~= 3) & (n == 3))
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lab = lab'
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end;
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xyz_k(2,:) = (lab(1,:) + 16)/116;
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xyz_k(1,:) = lab(2,:)/500 + xyz_k(2,:);
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xyz_k(3,:) = xyz_k(2,:) - lab(3,:)/200;
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xyz = f1(xyz_k);
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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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function xyz = f1(xyz_k)
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thresh_n = 0.008856;
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[idx_m, idx_n] = find(xyz_k.^3 > thresh_n);
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xyz(idx_m,idx_n) = xyz_k(idx_m,idx_n).^3;
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[idx_m, idx_n] = find(xyz_k.^3 <= thresh_n);
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xyz(idx_m,idx_n) = (xyz_k(idx_m,idx_n) - 16/116)/7.787;
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