Problem in creating movie

Question

Sneheet 2014-2-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/114651-problem-in-creating-movie

评论： Image Analyst 2018-9-20

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I am trying to create a movie from the frames previously extracted from 'rhinos.avi', which ships with MATLAB.

My current folder is the one containing these frames.

The frames are saved as 'Frame 0001.png','Frame 0002.png',.....'Frame 0114.png'.

Can someone please tell me what is wrong with my code?

vid=VideoWriter('sample.avi')
open(vid)
for i=1:9
      f1=strcat('Frame 000',num2str(i),'.png')
      writeVideo(vid,f1)
  end
for i=10:99
      f1=strcat('Frame 00',num2str(i),'.png')
      writeVideo(vid,f1)
end
for i=100:114
      f1=strcat('Frame 0',num2str(i),'.png')
      writeVideo(vid,f1)
  end
  close(vid)
movie(vid)

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Answer 1

Walter Roberson 2014-2-3

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You cannot writeVideo() a file name. You need to read the image from the file and write the result.

Note:

for i = 1 : 114
  f1 = sprintf('Frame %04d.jpg', i);
  ...
end

No need to construct the name 3 different ways.

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Sneheet 2014-2-4

alright, what does %04d mean?

Walter Roberson 2014-2-4

'd' for a "decimal" number (integer), 4 for output width of 4, 0 means to zero-fill from the beginning to the required width. In other words output a 4 digit number with leading 0's.

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Answer 2

Image Analyst 2014-2-4

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https://ww2.mathworks.cn/matlabcentral/answers/114651-problem-in-creating-movie#answer_123175

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But I already showed you how to do this in your original question. http://www.mathworks.com/matlabcentral/answers/114327#answer_122811 Here it is again:

  % Create a VideoWriter object to write the video out to a new, different file.
  writerObj = VideoWriter('NewRhinos.avi');
  open(writerObj);
  
  % Read the frames back in from disk, and convert them to a movie.
  % Preallocate recalledMovie, which will be an array of structures.
  % First get a cell array with all the frames.
  allTheFrames = cell(numberOfFrames,1);
  allTheFrames(:) = {zeros(vidHeight, vidWidth, 3, 'uint8')};
  % Next get a cell array with all the colormaps.
  allTheColorMaps = cell(numberOfFrames,1);
  allTheColorMaps(:) = {zeros(256, 3)};
  % Now combine these to make the array of structures.
  recalledMovie = struct('cdata', allTheFrames, 'colormap', allTheColorMaps)
  for frame = 1 : numberOfFrames
    % Construct an output image file name.
    outputBaseFileName = sprintf('Frame %4.4d.png', frame);
    outputFullFileName = fullfile(outputFolder, outputBaseFileName);
    % Read the image in from disk.
    thisFrame = imread(outputFullFileName);
    % Convert the image into a "movie frame" structure.
    recalledMovie(frame) = im2frame(thisFrame);
    % Write this frame out to a new video file.
    writeVideo(writerObj, thisFrame);
  end
  close(writerObj);

Obviously you can set the for loop to go from whatever starting frame number you want to whatever stopping frame number you want. When you tried to modify it (assuming you didn't ignore it) you replaced the frame with a string for some reason - bad news. Try to follow what I showed you as closely as you can and tell me if that works.

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Sneheet 2014-2-4

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I tried to separate out from your code the part that will only split the video into frames.

But the frames were all saved as blank images. I've attached an example.

The part of the code I used is:

    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
    % 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]);
      
      % Ask user if they want to write the individual frames out to disk.
      promptMessage = sprintf('Do you want to save the individual frames out to individual disk files?');
      button = questdlg(promptMessage, 'Save individual frames?', 'Yes', 'No', 'Yes');
      if strcmp(button, 'Yes')
        writeToDisk = true;
        
        % Extract out the various parts of the filename.
        [folder, baseFileName, extentions] = fileparts(movieFullFileName);
        % Make up a special new output subfolder for all the separate
        % movie frames that we're going to extract and save to disk.
        % (Don't worry - windows can handle forward slashes in the folder name.)
        folder = pwd;   % Make it a subfolder of the folder where this m-file lives.
        outputFolder = sprintf('%s/Movie Frames from %s', folder, baseFileName);
        % Create the folder if it doesn't exist already.
        if ~exist(outputFolder, 'dir')
          mkdir(outputFolder);
        end
      else
        writeToDisk = false;
      end
      
      % 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);
            if writeToDisk
          % Construct an output image file name.
          outputBaseFileName = sprintf('Frame %4.4d.png', frame);
          outputFullFileName = fullfile(outputFolder, outputBaseFileName);
          
          % Stamp the name and frame number onto the image.
          % At this point it's just going into the overlay,
          % not actually getting written into the pixel values.
          text(5, 15, outputBaseFileName, 'FontSize', 20);
          
          % Extract the image with the text "burned into" it.
          frameWithText = getframe(gca);
          % frameWithText.cdata is the image with the text
          % actually written into the pixel values.
          % Write it out to disk.
          imwrite(frameWithText.cdata, outputFullFileName, 'png');
            end
            % Update user with the progress.  Display in the command window.
        if writeToDisk
          progressIndication = sprintf('Wrote frame %4d of %d.', frame, numberOfFrames);
        else
          progressIndication = sprintf('Processed frame %4d of %d.', frame, numberOfFrames);
        end
        disp(progressIndication);
        % Increment frame count (should eventually = numberOfFrames
        % unless an error happens).
        numberOfFramesWritten = numberOfFramesWritten + 1;
        end
    end

What did I do wrong?

Image Analyst 2018-9-20

在 MATLAB Online 中打开

The main problem is that you were saving the current axes but you forgot to display an image in it with imshow(). The other problem is that the folder where MATLAB put rhinos.avi has changed since I posted this (from imdemos to imdata). I put in code to find the rhinos wherever they may live. Fixed code is below:

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
% Open the rhino.avi demo movie that ships with MATLAB.
% Let's let the user select from a list of all the demo images that ship with the Image Processing Toolbox.
folder = fileparts(which('rhinos.avi')); % Determine where demo folder is (works with all versions).
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]);
  
  % Ask user if they want to write the individual frames out to disk.
  promptMessage = sprintf('Do you want to save the individual frames out to individual disk files?');
  button = questdlg(promptMessage, 'Save individual frames?', 'Yes', 'No', 'Yes');
  if strcmp(button, 'Yes')
    writeToDisk = true;
    
    % Extract out the various parts of the filename.
    [folder, baseFileName, extentions] = fileparts(movieFullFileName);
    % Make up a special new output subfolder for all the separate
    % movie frames that we're going to extract and save to disk.
    % (Don't worry - windows can handle forward slashes in the folder name.)
    folder = pwd;   % Make it a subfolder of the folder where this m-file lives.
    outputFolder = sprintf('%s/Movie Frames from %s', folder, baseFileName);
    % Create the folder if it doesn't exist already.
    if ~exist(outputFolder, 'dir')
      mkdir(outputFolder);
    end
  else
    writeToDisk = false;
  end
  
  % 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);
    imshow(thisFrame);
    caption = sprintf('Frame #%d', frame);
    title(caption, 'FontSize', 15);
    drawnow;
    if writeToDisk
      % Construct an output image file name.
      outputBaseFileName = sprintf('Frame %4.4d.png', frame);
      outputFullFileName = fullfile(outputFolder, outputBaseFileName);
      
      % Stamp the name and frame number onto the image.
      % At this point it's just going into the overlay,
      % not actually getting written into the pixel values.
      text(5, 15, outputBaseFileName, 'FontSize', 20);
      
      % Extract the image with the text "burned into" it.
      frameWithText = getframe(gca);
      % frameWithText.cdata is the image with the text
      % actually written into the pixel values.
      % Write it out to disk.
      imwrite(frameWithText.cdata, outputFullFileName, 'png');
    end
    
    % Update user with the progress.  Display in the command window.
    if writeToDisk
      progressIndication = sprintf('Wrote frame %4d of %d.', frame, numberOfFrames);
    else
      progressIndication = sprintf('Processed frame %4d of %d.', frame, numberOfFrames);
    end
    disp(progressIndication);
    % Increment frame count (should eventually = numberOfFrames
    % unless an error happens).
    numberOfFramesWritten = numberOfFramesWritten + 1;
  end
end
fprintf('Done!\n');
helpdlg('Done!');

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Answer 3

shiva kumar 2018-9-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/114651-problem-in-creating-movie#answer_337616

vid=VideoWriter('sample.avi') open(vid) for i=1:9 f1=strcat('Frame 000',num2str(i),'.png') writeVideo(vid,f1) end for i=10:99 f1=strcat('Frame 00',num2str(i),'.png') writeVideo(vid,f1) end for i=100:114 f1=strcat('Frame 0',num2str(i),'.png') writeVideo(vid,f1) end close(vid) movie(vid)