how to find size of image compressed by principal component analysis??

Question

azizullah khan 2014-2-17

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/116476-how-to-find-size-of-image-compressed-by-principal-component-analysis

评论： azizullah khan 2014-2-19

采纳的回答： Image Analyst

i have compressed images/data by PCA,now i want to find size of the image that i have compressed by PCA????

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Image Analyst 2014-2-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/116476-how-to-find-size-of-image-compressed-by-principal-component-analysis#answer_124671

Each PC image will be the same number of rows and columns, though each pixel might be as many as 8 bytes instead of 1 if you're getting double arrays out and starting with uint8. So it may not be compressed at all. Anyway, it would depend on how many PC components there are. There could be 1, 2, 3, 4, 5, or whatever. How many are you calculating and keeping?

5 个评论
显示 3更早的评论隐藏 3更早的评论

azizullah khan 2014-2-17

在 MATLAB Online 中打开

36x36 is my input image and i have 14 images to compressed by PCA.In feature extraction i put only 13 eigen faces so my final data become 13x14 so how to find it... totalimage{1} upto totalimage{14} are my input images..

s=size(totalimage{1});

datamatrix=zeros(s(1)*s(2),numel(images));

for i= 1:numel(images)

datamatrix(:,i)=totalimage{i}(:);

end;

meanf=mean(datamatrix,2);

centermatrix=datamatrix-repmat(meanf,[1,numel(images)]);

%newcentermatrix=centermatrix';

[v,s,u]=princomp(centermatrix);

[u positions]=dsort(u);

%v=centermatrix*v;

eigenfaces=centermatrix*v;

for i=1:numel(images)

eigenfaces(:,i)=eigenfaces(:,i)/(norm(eigenfaces(:,i)));

end;

[m,n]=size(eigenfaces);

m=sqrt(m);

for i=1:18

%figure('name','Eigenfaces')

% figure(3),subplot(6,3,i),imshow(mat2gray(reshape(eigenfaces(:,i),m,m))),

%title('Eigenfaces');

end;

%figure('name','Eigen values'),plot(u);

%significantvalue=input('enter significant values=');

feature=eigenfaces(:,positions(1:1:numel(images)-1));

final=feature'*centermatrix;

now how to find that how much data i have compressed????thanks in advance...

Image Analyst 2014-2-18

The eigen images are computed just once for all images you want to model. Then for each image, you just need to save the weights applied to each eigenface image. So compression is happening because you're just saving a 1D vector of weights, not all the images. If you're taking 50 eigen images, then each image only needs to save 50 numbers. The eigen images themselves are not considered when you compute compression because they are just the same set of permanent images for all images you want to synthesize.

azizullah khan 2014-2-19

thanks sir,but i now want to plot compression vs threshold graph.So how i can change compression?

请先登录，再进行评论。

how to find size of image compressed by principal component analysis??

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

采纳的回答

5 个评论
显示 3更早的评论隐藏 3更早的评论

更多回答（0 个）

另请参阅

类别

标签

Community Treasure Hunt

how to find size of image compressed by principal component analysis??

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

采纳的回答

5 个评论 显示 3更早的评论隐藏 3更早的评论

更多回答（0 个）

另请参阅

类别

标签

Community Treasure Hunt

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

5 个评论
显示 3更早的评论隐藏 3更早的评论