Enhance the image with non-linear function

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Lara Adms
Lara Adms 2016-3-7
评论： Rena Berman 2017-1-24
Hello everyone, I'm a beginner in using Matlab and I want to know if what I did in solving this question right or wrong:
the question says:
Implement and test a method with the following specification. Input: A gray scale image Processing: Enhance the image with non-linear function Output: Enhanced image In the implementation follow the steps given below:
  • Read the image Im
  • The image will be in uint8 format. Convert it into double and transform the range of gray scale into [-1 1]. Call it TIm
  • Compute the max of the absolute values of the transformed image Tim i.e. max{|Tim|}.
  • Define a threshold as T = t x mean{|Tim|}, where t is user-defined and must be in the range (0,1). Try different values of t.
*Enhance the image using the following function:
where k > 1 is also user-defined. Try different values of k. Test different values of t and k to find the values which give the best enhancement results. Preparer a report showing the results with different values of t and k, and also write the comments on the behavior of these parameters for enhancement. __________
I solved the first four points as follows:
% Close images and clear the workspace, if there are any active contents
clc; clear all; close all;
% Read the image Im
Im = imread('noise_field.jpg');
%Convert it into double and transform the range of gray scale into [-1 1]
Imt = double(Im);
Tim = mat2gray(Imt, [-1, 1]);
%Compute the max of the absolute values of the transformed image Tim
MaxTim = max(abs(Tim));
%Define a threshold as T = t x mean{|Tim|}
t=double(0.1);
T= t*mean(Tim);
The last point I really have no idea about how to do it:(
Is my code correct?! I appreciate your help

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采纳的回答

Image Analyst
Image Analyst 2016-3-7
No. max() gives the max column-by-column so you need to transform it into a column vector:
% Compute the max of the absolute values of the transformed image Tim
MaxTim = max(abs(Tim(:)));
%Define a threshold as T = t x mean{|Tim|}
t = 0.1;
T = t*mean(Tim(:));
% Compute binary map of different intensity ranges
darkPixels = Tim < -T;
mediumPixels = abs(Tim) < T;
brightPixels = Tim > T;
% Now create a new image
enhancedTim = zeros(size(Tim));
% Assign dark pixels
enhancedTim(darkPixels) = Tim + (k-1)*T;
% Do the same for medium and bright pixels with their formulas.
To get t and k, adapt this:
% Ask user for two floating point numbers.
defaultValue = {'45.67', '78.91'};
titleBar = 'Enter a value';
userPrompt = {'Enter floating point number 1 : ', 'Enter floating point number 2: '};
caUserInput = inputdlg(userPrompt, titleBar, 1, defaultValue);
if isempty(caUserInput),return,end; % Bail out if they clicked Cancel.
% Convert to floating point from string.
usersValue1 = str2double(caUserInput{1})
usersValue2 = str2double(caUserInput{2})
% Check for a valid number.
if isnan(usersValue1)
% They didn't enter a number.
% They clicked Cancel, or entered a character, symbols, or something else not allowed.
% Convert the default from a string and stick that into usersValue1.
usersValue1 = str2double(defaultValue{1});
message = sprintf('I said it had to be a number.\nI will use %.2f and continue.', usersValue1);
uiwait(warndlg(message));
end
% Do the same for usersValue2
If you're still stumped, let me know.
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Lara Adms
Lara Adms 2016-3-7
编辑：Lara Adms 2016-3-7
Please sir can you till me how can I delete my question and if that is Ok with you
Walter Roberson
Walter Roberson 2016-3-8
No, questions will not be deleted once posted, not unless they violate the terms of the site. If you wanted private consultation you should have paid a private consultant.

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