Saving indexed tif images from for loop: Problem with file size.

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Avigdor
Avigdor 2014-11-20
评论： Image Analyst 2014-11-25
Hi, I have the following loop that takes a 32-bit 4D data set data(m,n,i,j) and outputs i*j indexed m by n images.
fid=fopen('myfile','rb','ieee-le');
data4D=fread(fid,'int32');
image_dir=pwd;
for i=1:size(data4D,3)
for k=1:size(data4D,4)
data3D=squeeze(abs(data4D(:,:,1:1:end,k)));
data2D=(mat2gray(squeeze(data3D(:,:,i))));
baseFileName = strcat( 'Image_', num2str(k) ...
, 'SubImage_', num2str(i),'.tif');
fullFileName = fullfile(image_dir,baseFileName);
imwrite(data2D, fullFileName);
end
end
This saves the images, but they are not the correct file size, or bit number. I have tried to use the Tiff function to save the images, but I must not be doing it incorrectly, because the images are saved, but they all look 100% black. Is there a Matlab master out there who can tune up this script?
Thanks?

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回答（1 个）

Image Analyst
Image Analyst 2014-11-21
I don't think TIFF can take pixels in the range 0-1. Well maybe it can with special options. But you're calling mat2gray so why not simply multiply it by 255 and cast to uint8?
data2D= uint8(255*mat2gray(squeeze(data3D(:,:,i))));
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Avigdor
Avigdor 2014-11-21
编辑：Image Analyst 2014-11-25
I'm reading the data in as int32. I don't want to change it. Just want to save the data without precision loss as image. I'm going by this chart:
Mapping the Matlab numeric type to ImageJ type
Matlab ImageJ image type
uint8 Grayscale 8-bit
int8 Grayscale 8-bit
uint16 Grayscale 16-bit
int16 Grayscale 16-bit
uint32 Grayscale 16-bit (Possible loss of precision)
int32 Grayscale 16-bit (Possible loss of precision)
uint64 Not allowed
int64 Not allowed
single Grayscale 32-bit
*double Grayscale 32-bit (Possible loss of precision)*
Image Analyst
Image Analyst 2014-11-25
Please answer my question about the original range of the data. It may well be that the upper bytes are not being used.
You say your code "takes a 32-bit 4D data set data(m,n,i,j)". What is the data type of "data"? Is it int32, uint32, or single? It's not double like you said above if it's only 32 bits. Double is 8 bytes or 64 bits.

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