Plot of a FFT complex image

Hi. I am plotted a FFT complex image and the plot y-axis is real numbers. How is imageJ interpreting this image?

Can you provide the output image you got and explain what plugin you used?? FFT will be a complex image, there are multiple ways to display it. If you give us s few more details it will be easier to help you.

Hi. Sorry I realize I didn’t provide sufficient information.
I computed the FFT of an image using ImageJ and obtained a stack of the real and imaginary component of the FFT. The first question is: does ImageJ conduct compression of the gray values, e.g. logarithmic scaling?
I then placed a line profile over the imaginary image and obtained real values, some negative and others with positive. What is the meaning of the positive and negative signs?