How does imflatfield work?

Question

Julia Kelly 2019-11-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/490691-how-does-imflatfield-work

评论： Arthur Redgate 2023-9-1

imgtemp20190829_081610.csv

在 MATLAB Online 中打开

What formula does the imflatfield function use when used with a matrix as input?

For example, I have an image of surface temperature (attached) = bad_img. If I apply

corr_img = imflatfield(bad_img,100);

How can I reproduce corr_img without using imflatfield? I know that the gaussian filter can be generated using

iblur=imgaussfilt(bad_img, 100);

But what are the next steps?

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

William Nitsch 2021-10-2

Iout = Iin * mean(gaussian_blurred_img)/gaussian_blurred_img

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

DGM 2021-10-2

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/490691-how-does-imflatfield-work#answer_799974

编辑：DGM 2021-10-2

在 MATLAB Online 中打开

William's comment is close. Probably close enough to be useful, but not quite exactly the same as what imflatfield() does.

A = imread('printedtext.png');
sigma = 30;
% this is the reference
output1 = imflatfield(A,sigma);
% this is a replication of the behavior
A = im2single(A); % non-double images are converted to single
% this is the default filter size, but it can be set explicitly too
blurred = imgaussfilt(A,sigma,'padding','symmetric','filtersize',2*ceil(2*sigma)+1);
output2 = A*mean(A(:),'omitnan')./blurred; % mean of A, not of blurred image
output2 = im2uint8(output2);
immse(output1,output2) % show that the results match
ans = 0

Bear in mind that if you want to exactly replicate the behavior, there are other things that happen (e.g. dealing with NaNs and Inf) that need to also be considered. You can always just open imflatfield() and read it.

EDIT: oof. This wouldn't be the first time I absentmindedly answered a dead question...