opening a .rec file

I have a .rec file which is supposed to be a reconstructed SPECT image of a point source. I am trying to open it up in matlab.

I have usually used the following generic way of opening image data files in matlab:

fid = fopen('filename.ext','r');
A = fread(fid,sizeA,precision);
imagesc(A)
colormap('gray')
axis image off

but this block of code does not open my .rec file in this case. It simply returns a blank gray screen with no image. I was told something about specifying the file format, but I'm not sure how to do this.

[Iain]

Do you know the precision? - What precision have you specified?

Have you tried plotting A with plot(A,'x')?

[richard]

I believe the precision is 45x45, these are the pixel dimensions for the gamma camera. I have not used the plot command. What is the 'x' string you have put down for it stand for?

[Iain]

 plot(A,'x') should pop up a figure with the values of "A" plotted as crosses (thats what 'x' was for) - I was trying to get you to find out if there was data in the file. - Which Image Analyst is trying to help you do as well.

[richard]

The A matrix is zero so as a result there are x's only at zero...

[Image Analyst]

Attach your image and code to read it so we can (perhaps) try to fix it.

Answer 1

[Image Analyst]

Richard,

No, precision would be something like '*uint8'. What you called precision is actually "sizeA" and would be sizeA = [45, 45]. So try

sizeA = [45, 45];
precision = '*uint8';
A = fread(fid,sizeA,precision);
imshow(A, [])
colormap('gray');
axis on;

[richard]

Oh yea, the precision I believe is float32, I'll try this

[richard]

The block of code you sent still doesn't pull up the .rec file, it pulls up a blank black figure. What you sent works for most of the data images I have worked with, but the .rec file is still giving me trouble

[Image Analyst]

Try changing the endian (machinefmt) and see if that helps. What is the range of the values you get back? Are you sure you're using [] in the imshow() call?

[richard]

Yea I tried changing the machine format to all those listed, the matrix I get for A is still all zeroes... do you think that this attachment would get me where I need to be? I got the M-file from this url: http://www.mathworks.com/matlabcentral/fileexchange/29344-read-medical-data-3d/content/ReadData3D.m

[Image Analyst]

It may. Looks like you need the fig file also since it's a GUIDE file. Try reading in A as bytes, or just opening it in notepad. Is it all zeros if you use either of those? If so, then the file actually is all zeros for some reason.