Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

Thread Subject:
Convert video to images

Subject: Convert video to images

From: mohammadreza motamedi

Date: 4 Sep, 2011 14:58:25

Message: 1 of 2

Dear all,

I have a problem, I need to convert video to images (MATLAB R2010a), I
have tried to convert with ''aviread'' , but it doesn't work,
Any one knows what can I do????

Many thanks,

Reza

Subject: Convert video to images

From: ImageAnalyst

Date: 5 Sep, 2011 08:42:31

Message: 2 of 2

On Sep 4, 4:58 pm, mohammadreza motamedi <madrez...@gmail.com> wrote:
> Dear all,
>
> I have a problem, I need to convert video to images (MATLAB R2010a), I
> have tried to convert with ''aviread''  ,  but it doesn't work,
> Any one knows what can I do????
>
> Many thanks,
>
> Reza

-----------------------------------------------------------------------------------------
See my demo:

% IMPORTANT: The newsreader may break long lines into multiple lines.
% Be sure to join any long lines that got split into multiple single
lines.
% These can be found by the red lines on the left side of your
% text editor, which indicate syntax errors, or else just run the
% code and it will stop at the split lines with an error.

% Demo macro to extract frames and get frame means from an avi movie
% and save individual frames to separate image files.
% 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

% Open the rhino.avi demo movie that ships with MATLAB.
movieFullFileName = 'C:\Program Files\MATLAB\R2010a\toolbox\images
\imdemos\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
mov = aviread(movieFullFileName);
% movie(mov);
% Determine how many frames there are.
numberOfFrames = size(mov, 2);
numberOfFramesWritten = 0;
% Prepare a figure to show the images in the upper half of the
screen.
figure;
screenSize = get(0, 'ScreenSize');
newWindowPosition = [1 screenSize(4)/2 - 70 screenSize(3)
screenSize(4)/2];
set(gcf, 'Position', newWindowPosition); % Maximize figure.
% set(gcf, 'Position', get(0,'Screensize')); % Maximize figure.

    % 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 = mov(frame).cdata;

        % Display it
        hImage = subplot(1,2,1);
        image(thisFrame);
        axis square;
        caption = sprintf('Frame %4d of %d.', frame, numberOfFrames);
        title(caption, 'FontSize', fontSize);
        drawnow; % Force it to refresh the window.

% Write the image array to the output file, if requested.
        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

% 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(1,2,2);
        hold off;
plot(meanGrayLevels, 'k-', 'LineWidth', 2);
        hold on;
        plot(meanRedLevels, 'r-');
        plot(meanGreenLevels, 'g-');
        plot(meanBlueLevels, 'b-');

        % 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.
        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

    % Alert user that we're done.
    if writeToDisk
        finishedMessage = sprintf('Done! It wrote %d frames to folder
\n"%s"', numberOfFramesWritten, outputFolder);
    else
        finishedMessage = sprintf('Done! It processed %d frames of
\n"%s"', numberOfFramesWritten, movieFullFileName);
    end
    disp(finishedMessage); % Write to command window.
    uiwait(msgbox(finishedMessage)); % Also pop up a message box.

    % Exit if they didn't write any individual frames out to disk.
    if ~writeToDisk
        return;
    end

    % Ask user if they want to read the individual frames from the
disk,
    % that they just wrote out, back into a movie and display it.
    promptMessage = sprintf('Do you want to recall the individual
frames\nback from disk into a movie?\n(This will take several
seconds.)');
    button = questdlg(promptMessage, 'Recall Movie?', 'Yes', 'No',
'Yes');
    if strcmp(button, 'No')
        return;
    end

    % Read the frames back in, and convert them to a movie.
    % I don't know of any way to preallocate recalledMovie.
    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);
    end
    % Get rid of old image and plot.
    delete(hImage);
    delete(hPlot);
    % Create new axes for our movie.
    subPlot(1, 3, 2);
    axis off; % Turn off axes numbers.
    title('Movie recalled from disk', 'FontSize', fontSize);
    % Play the movie in the axes.
    movie(recalledMovie);
    % Note: if you want to display graphics or text in the overlay
    % as the movie plays back then you need to do it like I did at
first
    % (at the top of this file where you extract and imshow a frame at
a time.)
    msgbox('Done with this demo!');

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

Tags for this Thread

No tags are associated with this thread.

What are tags?

A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.

Anyone can tag a thread. Tags are public and visible to everyone.

Contact us