104 lines
2.7 KiB
Matlab
104 lines
2.7 KiB
Matlab
function [normX, normY, meanShape, Transform] = ProcrustesAnalysis(x, y, options)
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% Translate all elements to origin and scale to 1
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normX = zeros(size(x));
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normY = zeros(size(y));
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for i = 1:size(x,1)
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offsetX = mean(x(i,:));
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offsetY = mean(y(i,:));
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Transform.offsetX(i) = offsetX;
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Transform.offsetY(i) = offsetY;
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normX(i,:) = x(i,:) - offsetX;
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normY(i,:) = y(i,:) - offsetY;
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% Get the Frobenius norm, to scale the shapes to unit size
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scale = norm([normX(i,:) normY(i,:)], 'fro');
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Transform.scale(i) = scale;
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normX(i,:) = normX(i,:)/scale;
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normY(i,:) = normY(i,:)/scale;
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end
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% Rotate elements untill all of them have the same orientation
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% the initial estimate of rotation would be the first element
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% if change is less than 1% stop (shouldn't take more than 2 steps)
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change = 0.1;
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meanShape = [ normX(1,:); normY(1,:) ]';
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Transform.Rotation = zeros(size(x,1),1);
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for i = 1:30
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% align all of the shapes to the mean shape
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% remember all orientations to get the mean one
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orientations = zeros(size(normX,1),1);
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for j = 1:size(x,1)
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% do SVD of mean * X'
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currentShape = [ normX(j,:); normY(j,:) ]';
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[U, ~, V] = svd( meanShape' * currentShape);
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rot = V*U';
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if(asin(rot(2,1)) > 0)
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orientations(j) = real(acos(rot(1,1)));
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else
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orientations(j) = real(-acos(rot(1,1)));
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end
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Transform.Rotation(j) = Transform.Rotation(j) + orientations(j);
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currentShape = currentShape * rot;
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normX(j,:) = currentShape(:,1)';
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normY(j,:) = currentShape(:,2)';
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end
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% recalculate the mean shape;
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oldMean = meanShape;
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meanShape = [mean(normX); mean(normY)]';
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% rotate the mean shape to mean rotation
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meanOrientation = mean(orientations);
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% Do this only the first time
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if(i==1)
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rotM = [ cos(-meanOrientation) -sin(-meanOrientation); sin(-meanOrientation) cos(-meanOrientation) ];
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meanShape = meanShape * rotM;
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end
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% scale mean shape to unit
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meanScale = norm(meanShape, 'fro');
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meanShape = meanShape*(1/meanScale);
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% find frobenious norm
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diff = norm(oldMean - meanShape, 'fro');
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if(diff/norm(oldMean,'fro') < change)
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break;
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end
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end
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% transform to tangent space to preserve linearities
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% get the scaling factors for each shape
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if(options.TangentSpaceTransform)
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scaling = [ normX normY ] * [ meanShape(:,1)' meanShape(:,2)']';
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for i=1:size(x,1)
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normX(i,:) = normX(i,:) * (1 / scaling(i));
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normY(i,:) = normY(i,:) * (1 / scaling(i));
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end
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end
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