add a moving image over a plotted trajectory

x = 0:pi/100:2*pi;
y = sin(x);
plot(x, y);
%i want my image to move in this way
alpaca = 'alpaca.png';   
[I,map,transparency] = imread(alpaca); 
%i have this code to remove the background of my image
%i tried using image sc but i couldnt get it to work
%thank you!

[Isobel Leikis]

Thank you, it worked perfectly!

[Sumit]

Please check attachment. according to that i want multiple image (stationary) along trajectory. How it can be done

[DGM]

I just gave you an example.

https://www.mathworks.com/matlabcentral/answers/1700190-how-to-plot-a-dot-as-a-sphere-like-those-in-originlab

Answer 1

[DGM]

Assuming you actually want it to move in real time, this should be a start

x = 0:pi/100:2*pi;
y = sin(x);
plot(x, y); hold on

%i want my image to move in this way
fname = 'alpaca.png';   
[inpict,~,alpha] = imread(fname); 
inpict = flipud(inpict); % necessary to keep image upright
alpha = flipud(alpha);
imgsize = [0.7 0.8]; % [x y] in plot coordinates

% get current coordinates for the image 
xx = [-0.5 0.5]*imgsize(1) + x(1);
yy = [-0.5 0.5]*imgsize(2) + y(1);
hi = image(xx,yy,inpict);
hi.AlphaData = alpha; % set alpha

% enforce axes extents
axis equal
xlim([0 2*pi] + [-0.5 0.5]*imgsize(1))
ylim([-1 1] + [-0.5 0.5]*imgsize(2))

for k = 1:numel(x)
    hi.XData = [-0.5 0.5]*imgsize(1) + x(k);
    hi.YData = [-0.5 0.5]*imgsize(2) + y(k);
    
    % wait
    pause(0.02)	
end

[ss]

Hi,

i have copied your code but the image does not display,

do you khnow the reason please?

thank you for your help

[DGM]

What version are you using?

Are you using the same image?

Is the code exactly the same, or have you made changes?

Are there any error messages?

If you changed the curve, you'll probably have to also change the xlim and ylim lines accordingly, otherwise the actual plot content will be out of frame.

[ss]

Can you help me please, i want to do this: A rectangle will appear on the screen. the user must click on the rectangle as quickly as possible for 60-70 seconds. and the rectangle(or any different image) appears in mouvement on the screen, when it appears(each time in different place), the user must click with the mouse and it's validated if he doesn't click it not valid

[DGM]

Is the rectangle following a predetermined path, or is it appearing in random locations? The latter case is likely less complicated to implement.

Either way, it's probably best to open a new question for this. If you're intending to do this with Psychtoolbox, make sure to mention your intent.

[ss]

Thank you for your answer, yes it can be random locations

[Ashley]

This is probably the best demonstration of a sprite being used in Matlab so far.

Is it possible to make a sprite like this which the user can drag to different areas of the grid?

[DGM]

Probably. I'm not really sure of what the best way to do that would be. It may require setting up some interaction callbacks. I don't think I've ever tried to do this sort of thing specifically. I generally avoid interactive graphics as much as I can.

Answer 2

[Voss]

Something like this?

x = 0:pi/100:2*pi;
y = sin(x);

figure();
plot(x, y);
hold on
xlim([0 2*pi]);
ylim([-1 1]);

I = imread('alpaca.png');
im = image(I,'XData',[0 1],'YData',[0 1]);
for ii = 1:numel(x)
    set(im,'XData',x(ii)+[-0.5 0.5],'YData',y(ii)+[-0.5 0.5]);
    drawnow();
end

[ss]

hi, the same problem, the image does not display when i copied your code

did you khow why please?

[Voss]

Do you have the image file alpaca.png?

[ss]

Hi, last time it worked bu now it gives me this error

Subscript indices must either be real positive integers or logicals

Error in mouvement_sinusoidal (line 14)

im = image(I,'XData',[0 1],'YData',[0 1]);

[Voss]

Try doing

clear image

and then running it again.

That is, you may have a variable called image in your workspace that needs to be cleared before you can use the image function.

[ss]

yes it works! thank you a lot