Analysing frequency components

Hi,

which frequency components are responsible for texture in an image?

I heard lot of people saying high frequency components are resposible for texture in an image

But how?

I cannot find anything except complex values and spectrum by using fft2 command

How this can be analysed from the fft

Can anybody suggest something about this?

Thanks in advance

Answer 1

[Walter Roberson]

Why don't you construct an artificial image and start playing?

bar = zeros(64,64,'uint8');
bar(:) = 128;
bar(:,10:10:end) = 255;
bar(10:10:end,:) = 255;
colormap(gray(256));
imagesc(bar);

Now you can start exploring the fft() and fft2() properties with a "best-case" image.

foo = fft2(bar);
DC = foo(1,1); 
foo(1,1) = 0;
imagesc(real(foo));

What do you see? Can you explain why?

Answer 2

[Image Analyst]

Yeah but that lot of people may not know what they're talking about, or you may have oversimplified what they said. We talked about this before, remember? Remember when I explained how periodic texture will show up as periodic patterns (i.e. spikes) in the spectrum. Walter's suggestion of playing around with different images to see their spectrum is a good one.