Plot a line over every frame in a for loop

Experts,

I extracted the frames from a video and detected the edges of the moving object. Then drew a line that passes from the very top pixel of the boundary. I want the line to appear on every frame,However, the line only appears for the last frame.In addition, I need to label the y value of the line as well. Can you please help me. Here is the code and the image. I added the yellow arrow on the image with powerpoint to be clear. The left frame is missing the line and the image in the right is the last frame which has a line.

if true
  for i=1:10
  FileName=strcat(num2str(i),'.jpg');
  Im=imread(FileName);
  Im=imcrop(Im,[600 100 500 500]);
  Im = im2double(Im);
  Im=im2bw(Im,0.8);
  Im = edge(Im,'Sobel');
  imshow(Im)
  [y, x] = find(Im);
  H(w)=min(y);
  w=w+1;
  line([0 length(Im)], [min(y) min(y)])

end

end

Answer 1

[Kai Domhardt]

You need to a pause inbetween frames, before the next imshow(Im) executes.

Adding

pause(0.1)

as the final line inside your for-loop will solve your problem and display every frame for 0.1 seconds.

[Tala Hed]

Awesome. Any suggestion regarding labeling the line? I mean a legend comes beside it and says the distance between x axis and the line?

[Kai Domhardt]

You could do something like

font_size = 14;
text(0, font_size, ['Height: ' num2str(min(y))], 'Color', 'white','FontSize',font_size)

[Tala Hed]

Perfect . Thanks