Customize "implay"

function videofig_mod
%   based on João Filipe Henriques, 2010
videofile='xylophone.mp4'; %default video file, available in image processing toolbox
%videofile='VOK Animation.24.avi';
big_scroll = 30;
click = 0;
f = 1;  %current frame
fig_handle = figure('Color',[.3 .3 .3], 'MenuBar','none', 'Toolbar','none', 'Units','norm', ...
    'WindowButtonDownFcn',@button_down, 'WindowButtonUpFcn',@button_up, ...
    'WindowButtonMotionFcn', @on_click,'KeyPressFcn', @key_press,'Name','Video preview','numbertitle','off');
v = VideoReader(videofile);
play_fps = v.FrameRate;
num_frames=v.NumFrames;
%axes for scroll bar
scroll_axes_handle = axes('Parent',fig_handle, 'Position',[0 0 1 0.04], ...
    'Visible','off', 'Units', 'normalized');
axis([0 1 0 1]);
axis off
%scroll bar
scroll_bar_width = max(1 / num_frames, 0.02);
scroll_handle = patch([0 1 1 0] * scroll_bar_width, [0 0 1 1], [.8 .8 .8], ...
    'Parent',scroll_axes_handle, 'EdgeColor','none', 'ButtonDownFcn', @on_click);
%timer to play video
play_timer = timer('TimerFcn',@play_timer_callback, 'ExecutionMode','fixedRate');
%main drawing axes for video display
axes_handle = axes('Position',[0 0.07 1 0.9]);
%return handles
scroll_bar_handles = [scroll_axes_handle; scroll_handle];
scroll_func = @scroll;
h_fig=imshow(read(v,1));drawnow
set(fig_handle,'units','characters')
set(scroll_axes_handle,'units','characters')
%framenrdisplay
frametext = uicontrol(fig_handle,'Style','text','units', 'characters','Horizontalalignment', 'left','position',[0,1.1,20,1],'String',['Frame Nr.: 1/' num2str(num_frames)]);
    function key_press(src, event)  %#ok, unused arguments
        switch event.Key  %process shortcut keys
            case 'leftarrow'
                scroll(f - 1);
            case 'rightarrow'
                scroll(f + 1);
            case 'pageup'
                if f - big_scroll < 1  %scrolling before frame 1, stop at frame 1
                    scroll(1);
                else
                    scroll(f - big_scroll);
                end
            case 'pagedown'
                if f + big_scroll > num_frames  %scrolling after last frame
                    scroll(num_frames);
                else
                    scroll(f + big_scroll);
                end
            case 'home'
                scroll(1);
            case 'end'
                scroll(num_frames);
            case 'return'
                play(1/play_fps)
            case 'backspace'
                play(5/play_fps)
        end
    end
%mouse handler
    function button_down(src, event)  %#ok, unused arguments
        set(src,'Units','norm')
        click_pos = get(src, 'CurrentPoint');
        if click_pos(2) <= 0.03  %only trigger if the scrollbar was clicked
            click = 1;
            on_click([],[]);
        end
    end
    function button_up(src, event)  %#ok, unused arguments
        click = 0;
    end
    function on_click(src, event)  %#ok, unused arguments
        if click == 0, return; end
        
        %get x-coordinate of click
        set(fig_handle, 'Units', 'normalized');
        click_point = get(fig_handle, 'CurrentPoint');
        set(fig_handle, 'Units', 'pixels');
        x = click_point(1);
        
        %get corresponding frame number
        new_f = floor(1 + x * num_frames);
        
        if new_f < 1 || new_f > num_frames, return; end  %outside valid range
        
        if new_f ~= f  %don't redraw if the frame is the same (to prevent delays)
            if new_f<num_frames
                try
                    scroll(new_f);
                catch
                end
            end
            
        end
    end
    function play(period)
        %toggle between stoping and starting the "play video" timer
        if strcmp(get(play_timer,'Running'), 'off')
            set(play_timer, 'Period', period);
            start(play_timer);
        else
            stop(play_timer);
        end
    end
    function play_timer_callback(src, event)  %#ok
        %executed at each timer period, when playing the video
        if f < num_frames
            scroll(f + 1);
        elseif strcmp(get(play_timer,'Running'), 'on')
            stop(play_timer);  %stop the timer if the end is reached
        end
    end
    function scroll(new_f)
        if nargin == 1  %scroll to another position (new_f)
            if new_f < 1 || new_f > num_frames
                return
            end
            f = new_f;
        end
        
        %convert frame number to appropriate x-coordinate of scroll bar
        scroll_x = (f - 1) / num_frames;
        
        %move scroll bar to new position
        set(scroll_handle, 'XData', scroll_x + [0 1 1 0] * scroll_bar_width);
        
        %set to the right axes and call the custom redraw function
        set(fig_handle, 'CurrentAxes', axes_handle);
        
        h_fig.CData = read(v,f);
        set (frametext,'String', ['Frame Nr.: ' int2str(f) '/' int2str(num_frames)])
        
        %used to be "drawnow", but when called rapidly and the CPU is busy
        %it didn't let Matlab process events properly (ie, close figure).
        pause(0.001)
        %drawnow limitrate
    end
end

Walter Roberson 2020-12-8

Sometimes video_fig is a very convenient contribution for customizing !

William Thielicke 2020-12-8

I uploaded the modification here, because I think this is useful for other people too (and I think the original videofig is less straight forward for people to use):

https://de.mathworks.com/matlabcentral/fileexchange/84028-preview-and-play-video-files

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