Writing images using imwrite- Getting white images

Question

I am writing a function that generates series of images. I am using the imwrite function to write each image to a file:

Ecc=sqrt(real(E(:,:,1)).^2+real(E(:,:,2)).^2+real(E(:,:,3)).^2+imag(E(:,:,1)).^2+imag(E(:,:,2)).^2+imag(E(:,:,3)).^2);
clf

Q=imagesc(nx/rad,ny/rad,Ecc); 
    if i==1
    cl=caxis;
    else
    caxis(cl)
    end
imwrite(Q,['Frame-',num2str(i),'.tif'],'tif');

But I am not getting the images. The files are generated just fine, but they are just white images with dimension 1x1. Any help please? Thank you

Answer 1

Use imwrite on Ecc instead of Q . The output of imagesc (as I recall) is a handle to the figure, which is not what you want to write out. Write out Ecc instead.

Answer 2

Adding to what user3817401 has written.

Completly white images can result from data not being scaled prior to being sent to imwrite. Consider following:

Ecc = (Ecc - min(min(Ecc))) / (max(max(Ecc)) - min(min(Ecc)));

promply before imwrite. This will guarantee, that the image is in range 0-1 and should solve the problem.

Answer 3

The function imagesc returns a handle (you store it as Q), not scaled image data. Then, the function imwrite is interpreting Q as an image. Because it is a handle, it is just 1x1 and it's value is not meaningful as an image. Try scaling Ecc as desired and then writing that instead.