04-1 - Frequency domain filtering fundamentals

04-1 - Frequency domain filtering fundamentals - 4/28/2008

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
4/28/2008 1 Frequency domain filtering fundamentals Spring 2008 ELEN 4304/5365 DIP 1 by Gleb V. Tcheslavski: gleb@ee.lamar.edu http://ee.lamar.edu/gleb/dip/index.htm Preliminaries For a digital image f ( x,y ) the basic filtering equation is 1 { } (, ) (,) (,) gxy HuvFuv = ℑ Where H ( u,v ) and F ( u,v ) are DFTs of the image and of the filter. Their product is defined by array (element-by-element) multiplication. Specifications of H ( u,v ) are simplified considerably when using functions symmetric about their centers This requires Spring 2008 ELEN 4304/5365 DIP 2 when using functions symmetric about their centers. This requires that F ( u,v ) is also centered, which is accomplished by multiplying the input image by (-1) x+y before computing its transform.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4/28/2008 2 Simple filters Considering the following image with centered (and scaled) DFT Spring 2008 ELEN 4304/5365 DIP 3 Simple filters One of the simplest filters would be H ( u,v ) having 0 at the center and 1 elsewhere. Such filter will reject the DC (constant) term and l thi l h d leave everything else unchanged. Since the DC term represents an average intensity, setting it to zero results in reduction of average intensity to zero. Spring 2008 ELEN 4304/5365 DIP 4 Therefore, the resulting image appears darker. Actually, aero average implies negative intensities.
Background image of page 2
4/28/2008 3 Simple filters Low frequencies in the transform are related to slowly varying intensity components of image. High frequencies are caused by
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 8

04-1 - Frequency domain filtering fundamentals - 4/28/2008

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online