I hope you are looking for something like this.
1) First create a folder named 'Frames'(without quotes) in your current directory.
Then you can do the following part :
close all
clear all
clc
delete('Frames\*.jpg');
[filename pathname] = uigetfile({'*.avi'},'Select A Video File');
I = VideoReader([pathname,filename]);
implay([pathname,filename]);
pause(3);
nFrames = I.numberofFrames;
vidHeight = I.Height;
vidWidth = I.Width;
mov(1:nFrames) = ...
struct('cdata', zeros(vidHeight, vidWidth, 3, 'uint8'),...
'colormap', []);
WantedFrames = 50;
for k = 1:WantedFrames
mov(k).cdata = read( I, k);
mov(k).cdata = imresize(mov(k).cdata,[256,256]);
imwrite(mov(k).cdata,['Frames\',num2str(k),'.jpg']);
end
