Problem with creating .bmp images
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Hi, all
I'm running PCA on ORL human face image database. What I want to achieve it to extract the principal components, then add the mean vector back to these component. By writing these components as .bmp images, I can get eigen faces. Here is my code
clc
clear all
close all
path = 'D:\\Matlab 7.0\\work\\ORL\\';
data = zeros(400, 10304);
for i = 1:400
name = [path 'face' num2str(i) '.bmp'];
temp = imread(name);
temp = reshape(temp, 1, 10304);
data(i, :) = temp;
end
meanface = mean(data, 1);
data = data - repmat(meanface, 400, 1);
intermat = (data * data') / (400-1);
[intervec, val] = eig(intermat);
pc = data'*intervec;
pc = pc';
for i = 1:400
pc(i,:) = pc(i,:) / sqrt(dot(pc(i,:), pc(i,:)));
sd(i) = sqrt(val(i,i));
eigenvalue(i) = val(i,i);
end
pc = flipud(pc);
sd = fliplr(sd);
eigenvalue = fliplr(eigenvalue);
%%%%%%Write images %%%%%%%
for i = 1:399
mode = pc(i,:) + meanface;
mode = round(mode);
mode = reshape(mode, 112, 92);
name = ['pc' num2str(i) '.bmp'];
imwrite(mode, name, 'bmp');
end
I was expecting to see ghost-like images. However, this piece of code writes images that all white.
May I know if there is anything wrong with my code?
Thank you very much for your kindly help.
Best regards Wenlong
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Answers (1)
Image Analyst
on 21 Sep 2012
I don't believe BMP supports floating point. If you want floating point, save as .mat. If you want a standard BMP, then cast to uint8 before saving, though beware that you may lose numerical resolution as it will truncate the values and may require scaling and shifting into the 0-255 value range.
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