Unsharp filter: Matlab

Posted on 2009-03-29
Last Modified: 2016-02-10
I need to make an unsharp filter using following parameters:
%gaussian_size     size of the applied filter
&gaussian_std      standard deviation of the gaussian filter, sigma
for an image. in the folder images.
Following functions must be implemented:
Input:      <RGB frames>, Filterparameter
Output;    filtered <RGB frames>
Data: filter_unsharp.m

Would be grateful for your help
Question by:ihbemd6rb

Expert Comment

ID: 24015099
The basic setup is:

I = imread('cameraman.tif');
H = fspecial('unsharp');
sharpened = imfilter(I,H,'replicate');
imshow(sharpened); title('Sharpened Image');

You can pass other options to fspecial (the filter parameters). Take a look at
doc fspecial
in Matlab. I'm assuming you have the Image Processing Toolbox?


Author Comment

ID: 24017111
Hello and thanks for the answer, I have already seen this code on the mathworks website. My problem is how to make this function from it:
 function video = filter_unsharp(video, gaussian_size, gaussian_std);
As an example something similar to this:
function video = filter_rand_illumination(video, min_brightness, max_brightness)
    RGB = video.frame(1).filtered;
    HSV = rgb2hsv(RGB);
     luma_factor = 0;
          while(luma_factor < min_brightness || luma_factor > max_brightness)
           luma_factor = rand(1);
      v = HSV(:,:,3);
      hue_v = v * luma_factor;
      HSV(:,:,3) = hue_v;
RGB = hsv2rgb(HSV);
 video.frame(1).filtered = RGB;
This is just an example of how do I need to construct unsharp filter.

LVL 15

Accepted Solution

yuk99 earned 500 total points
ID: 24022453
AFAIK unsharp filter in Matlab does not use gaussian smoothing. It subtracts laplacian filter (with parameter ALPHA, which controls laplacian shape) from the original image.
If you  need to use those gaussian parameters, you'll have to develop your own filter function. Once you have it, run imfilter on separate frames within for-loop. Somethig like
H = fspecial('unsharp');
for i=1_numel(video)
    video2(i).cdata = imfilter(video(i).cdata,H,'replicate');


Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
WPF issue with Trigger 2 115
Re-position the objects 7 117
Problem to error 4 67
Just learning algebra / need solution explained 4 59
We are taking giant steps in technological advances in the field of wireless telephony. At just 10 years since the advent of smartphones, it is crucial to examine the benefits and disadvantages that have been report to us.
When we purchase storage, we typically are advertised storage of 500GB, 1TB, 2TB and so on. However, when you actually install it into your computer, your 500GB HDD will actually show up as 465GB. Why? It has to do with the way people and computers…
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
Finds all prime numbers in a range requested and places them in a public primes() array. I've demostrated a template size of 30 (2 * 3 * 5) but larger templates can be built such 210  (2 * 3 * 5 * 7) or 2310  (2 * 3 * 5 * 7 * 11). The larger templa‚Ķ

828 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question