Prof. Saravanan Vijayakumaran Image Averaging Smoothing is often used to reduce noise within an image. Most smoothing methods are based on low pass filters. Course Name: Digital Image Processing Level: UG Authors Phani Swathi Chitta Mentor Prof. Saravanan Vijayakumaran *The contents in this ppt are licensed under Creative Commons Attribution-NonCommercial-ShareAlike 2.5 India license

Learning Objectives After interacting with this Learning Object, the learner will be able to: Explain how the averaging of an image is done

1 2 3 4 5 Definitions of the components/Keywords: In Smoothing, the value of every pixel in an image is replaced by the average of the intensity levels in the neighborhood defined by the filter mask. These filters are also called averaging filters. The smoothing process results in an image with reduced “sharp” transitions in intensities. The 3x3 smoothing filter that yields the standard average of the pixels under the mask is given below: 2 3 4 5 3

1 2 3 4 5 Definitions of the components/Keywords: A spatial averaging filter in which all coefficients are equal is called a box filter. Smoothing filters have to compromise noise reduction with edge blurring. 2 3 4 5

Master Layout 1 Original Image before filtering Image after filtering 2 3 4 Give a drop down box so that user can select any one filter size. The filter sizes must be 3x3, 5x5, 7x7 5

3 Step 1: 1 2 4 5 3x3 filter Instruction for the animator Text to be displayed in the working area (DT) The first fig. should appear and then when the 3x3 filter size from the dropdown box is selected then enable start button After start button is clicked show the second figure The text in DT should appear in parallel to the figures The original image The resulting image is the image filtered with 3x3 averaging mask 5

3 Step 2: 1 2 4 5 5x5 Instruction for the animator Text to be displayed in the working area (DT) The first fig. should appear and then when the 5x5 filter size from the dropdown box is selected then enable start button After start button is clicked show the second figure The text in DT should appear in parallel to the figures The original image The resulting image is the image filtered with 5x5 averaging mask 5

3 Step 3: 1 2 4 5 7x7 Instruction for the animator Text to be displayed in the working area (DT) The first fig. should appear and then when the 7x7 filter size from the dropdown box is selected then enable start button After start button is clicked show the second figure The text in DT should appear in parallel to the figures The original image The resulting image is the image filtered with 7x7 averaging mask 5

Test your understanding Electrical Engineering Slide 1 Slide 3 Slide 10, 11,12 Slide 13 Introduction Definitions Analogy Test your understanding (questionnaire)‏ Lets Sum up (summary)‏ Want to know more… (Further Reading)‏ Interactivity: Try it yourself Select any one of the figures a b c d Select the filter size 9 Credits 9

Questionnaire 1 1.What is the value of the yellow box after smoothing is done? Answers: a) 3 b) 1 c) 4 d)‏ 9 2 3 4 5

Questionnaire 1 2. What are the values of yellow boxes after smoothing filter is applied? Answers: a) b) 2 3 4 5

Questionnaire 1 2. What are the values of yellow boxes after smoothing filter is applied? Answers: c) d) 2 3 4 5

Links for further reading Reference websites: http://idlastro.gsfc.nasa.gov/idl_html_help/Smoothing_an_Image.html Books: Digital Image Processing- Rafael C. Gonzalez, Richard E. Woods, second edition, Pearson Education Research papers: