How do I write entropyfilt code for a video?

I want to calculate entropyfilt for a video.First I read a video and show frames then I want to calculate entropyfilt for some frames or all frames. I read MATLAB help but I cant find out!

How do I write the code?

Answer 1

[Image Analyst]

Run my demo:

% Demo macro to extract frames and get frame means from an avi movie
% and entropy-filter the individual frames.
% Also computes the mean gray value of the color channels.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 14;

% Change the current folder to the folder of this m-file.
% (The line of code below is from Brett Shoelson of The Mathworks.)
if(~isdeployed)
  cd(fileparts(which(mfilename)));
end

% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
  % User does not have the toolbox installed.
  message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
  reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
  if strcmpi(reply, 'No')
    % User said No, so exit.
    return;
  end
end

% Open the rhino.avi demo movie that ships with MATLAB.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
movieFullFileName = fullfile(folder, 'rhinos.avi');
% Check to see that it exists.
if ~exist(movieFullFileName, 'file')
  strErrorMessage = sprintf('File not found:\n%s\nYou can choose a new one, or cancel', movieFullFileName);
  response = questdlg(strErrorMessage, 'File not found', 'OK - choose a new movie.', 'Cancel', 'OK - choose a new movie.');
  if strcmpi(response, 'OK - choose a new movie.')
    [baseFileName, folderName, FilterIndex] = uigetfile('*.avi');
    if ~isequal(baseFileName, 0)
      movieFullFileName = fullfile(folderName, baseFileName);
    else
      return;
    end
  else
    return;
  end
end

try
  videoObject = VideoReader(movieFullFileName)
  % Determine how many frames there are.
  numberOfFrames = videoObject.NumberOfFrames;
  vidHeight = videoObject.Height;
  vidWidth = videoObject.Width;
  
  numberOfFramesWritten = 0;
  % Prepare a figure to show the images in the upper half of the screen.
  figure;
  %   screenSize = get(0, 'ScreenSize');
  % Enlarge figure to full screen.
  set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
  
  % Loop through the movie, writing all frames out.
  % Each frame will be in a separate file with unique name.
  meanGrayLevels = zeros(numberOfFrames, 1);
  meanRedLevels = zeros(numberOfFrames, 1);
  meanGreenLevels = zeros(numberOfFrames, 1);
  meanBlueLevels = zeros(numberOfFrames, 1);
  for frame = 1 : numberOfFrames
    % Extract the frame from the movie structure.
    thisFrame = read(videoObject, frame);
    
    % Display it
    hImage = subplot(2, 2, 1);
    image(thisFrame);
    caption = sprintf('Frame %4d of %d.', frame, numberOfFrames);
    title(caption, 'FontSize', fontSize);
    drawnow; % Force it to refresh the window.
    
    % Calculate the mean gray level.
    grayImage = rgb2gray(thisFrame);
    meanGrayLevels(frame) = mean(grayImage(:));
    
    % Calculate the mean R, G, and B levels.
    meanRedLevels(frame) = mean(mean(thisFrame(:, :, 1)));
    meanGreenLevels(frame) = mean(mean(thisFrame(:, :, 2)));
    meanBlueLevels(frame) = mean(mean(thisFrame(:, :, 3)));
    
    % Plot the mean gray levels.
    hPlot = subplot(2, 2, 2);
    hold off;
    plot(meanGrayLevels, 'k-', 'LineWidth', 2);
    hold on;
    plot(meanRedLevels, 'r-');
    plot(meanGreenLevels, 'g-');
    plot(meanBlueLevels, 'b-');
    grid on;
    
    % Put title back because plot() erases the existing title.
    title('Mean Gray Levels', 'FontSize', fontSize);
    if frame == 1
      xlabel('Frame Number');
      ylabel('Gray Level');
      % Get size data later for preallocation if we read
      % the movie back in from disk.
      [rows columns numberOfColorChannels] = size(thisFrame);
    end
    
    % Update user with the progress.  Display in the command window.
    progressIndication = sprintf('Processed frame %4d of %d.', frame, numberOfFrames);
    disp(progressIndication);
    % Increment frame count (should eventually = numberOfFrames
    % unless an error happens).
    numberOfFramesWritten = numberOfFramesWritten + 1;
    
    % Now let's do the entropy filter.
    % First get a gray level image
    grayImage = rgb2gray(thisFrame);
    subplot(2, 2, 3);
    imshow(grayImage);
    caption = sprintf('Gray Scale Image, frame #%d', frame);
    title(caption, 'FontSize', fontSize);
    % Display the filtered image.
    entropyFilteredImage = entropyfilt(grayImage);
    subplot(2, 2, 4);
    imshow(entropyFilteredImage, []);
    caption = sprintf('Entropy Filtered Image, frame #%d', frame);
    title(caption, 'FontSize', fontSize);
  end
  
  % Alert user that we're done.
  finishedMessage = sprintf('Done!  It processed %d frames of\n"%s"', numberOfFramesWritten, movieFullFileName);
  disp(finishedMessage); % Write to command window.
  uiwait(msgbox(finishedMessage)); % Also pop up a message box.
  
catch ME
  % Some error happened if you get here.
  stError = lasterror;
  strErrorMessage = sprintf('Error extracting movie frames from:\n\n%s\n\nError: %s\n\n)', movieFullFileName, stError.message);
  uiwait(msgbox(strErrorMessage));
end

[maria aa]

I want to choose one frame or some frames, then with using entropyfilt for frame,I want to divide that frame to square parts and choose some parts with high information (not uniform part)! Because of this I have to chose one frame or some frames.If it possible to choose frame please help me. Thanks

[Image Analyst]

I thought I did give you help - a lot of it. Basically I did your whole original question for you. I'll give you a little more guidance though with this additional request ... To select pixels with high entropy in any particular frame, you can threshold:

highEntropy = entropyFilteredImage > someThresholdValue1;

To select frames with overall high entropy, take the mean

if mean2(entropyFilteredImage) > someThresholdValue2
  % It's a high entropy frame
  listOfHighEntropyFrames = frame; % Record the frame number of this frame.
end

Is this enough to get you going now?

[maria aa]

Thanks for your answer.It is very useful ,but I don't know how I find the highest value?I read in an article that explained with thresholding procedure they could find low information pixels, medium information pixels and high information pixels but I don't know how?What is "someThresholdValue"? Thanks a lot

[Image Analyst]

maria, let's say you looked at the range of values in your entropy image, and let's say they went from 30 to 20,000. Now you have to divide that range up into low, medium, and high entropy values. You have to make that decision. Would you put the dividing lines at 1000 and 10,000? So that everything above 10,000 is "high" and everything below is "low" and everything in between is "medium". Or would you pick different thresholds to divide the low, medium, and high zones? I don't know what value you would pick - it's somewhat subjective. But whatever you pick, that's what I call someThresholdValue2. And you decide whether than number should be 100, 500, or 15000. Just try some values and see how the image looks - there is no "right" answer.

[maria aa]

Thanks a lot for your answer.You wrote this: "to select pixels with high entropy in any particular frame, you can threshold:". For example if I add this part in your code:

highEntropy = entropyFilteredImage > 10000; How can I show that pixels in image?You said with this code I could find the pixel with high entropy.If it possible please help me.I don't know how?

[Walter Roberson]

ImageCopy = YourImage;
ImageCopy(~highEntropy) = 0;
image(ImageCopy)

[maria aa]

Thanks for your answer.