Dark image using imshow

Hello,

I'm having a problem with imshow. I'm going point per point through my data and want to plot the corresponding video while I do this.

The file works when there is no video in it. And in another file I was able to plot the whole data with the video playing.

BUT: now when I use "animatedline" with "addpoints" the video is black. The video is black and becomes lighter sometimes, but you can't see anything.I have added a screenshot of the figure while its going through the data in the attachment.

UPDATE: when i remove all the animatedlines and addpoints the video plays correctly

Here is my code

%code

daqrate = 40;
VID = VideoReader('Zwemvideo1.mp4','Tag','My reader object');
writerObj = VideoWriter('output_video','MPEG-4');
writerObj.FrameRate = 40;
fps=30;%VID.FrameRate;
totalframes=VID.NumberOfFrames;
rate=daqrate/fps;

frameA=read(VID,1); 
x=[329 752];
y=[50 411];%56
ratio =(y(2)-y(1))/(x(2)-x(1));

acc_y = resample(acc_y,3,4);
acc_z = resample(acc_z,3,4);
gyr_y = resample(gyr_y,3,4);
gyr_x = resample(gyr_x,3,4);

figure
subplot(5,1,1)
xlabel('samples')
ylabel('gyr_x filtered')
title('Turn detection')
h = animatedline;
axis([0 length(gyr_x) -230 330])
x = linspace(0,length(gyr_x),length(gyr_x));

subplot(5,1,2)
xlabel('samples')
ylabel('acc_z filtered')
title('Stroke detection')
g = animatedline;
axis([0 length(acc_z) -1 1.5])
y = linspace(0,length(acc_z),length(acc_z));

subplot(5,1,3)
xlabel('samples')
ylabel('gyr_y filtered')
title('Stroke detection')
f = animatedline;
axis([0 length(gyr_y) -100 140])
z = linspace(0,length(gyr_y),length(gyr_y));

subplot(5,1,4)
xlabel('samples')
ylabel('acc_y filtered')
title('Stroke detection')
e = animatedline;
axis([0 length(acc_y) -2 2])
w = linspace(0,length(acc_y),length(acc_y));

for i = 1: length(gyr_x)

        %video
        drawnow
        subplot(5,1,5)

        frame= read(VID,1+i-1); 
        imshow(frame(y(1):y(2),x(1):x(2),:),[]);

        %rest
        gyr_x_memory= gyr_x(1:i);
        gyr_x_lowpass = [gyr_x_lowpass lowpass_filter(32,gyr_x_memory,gyr_x_lowpass)];%32
        %gyr_x_lowpass=abs(gyr_x_lowpass);
        gyr_y_memory= gyr_y(1:i);
        gyr_y_lowpass = [gyr_y_lowpass lowpass_filter(20,gyr_y_memory,gyr_y_lowpass)];
        %gyr_y_lowpass=abs(gyr_y_lowpass);
        acc_z_memory= acc_z(1:i);
        acc_z_lowpass = [acc_z_lowpass lowpass_filter(20,acc_z_memory,acc_z_lowpass)];
        %acc_z_lowpass=abs(acc_z_lowpass);
        acc_y_memory= acc_y(1:i);
        acc_y_lowpass = [acc_y_lowpass lowpass_filter(64,acc_y_memory,acc_y_lowpass)];%20->30 meer gesmooth
        addpoints(h,x(i),gyr_x_lowpass(i));
        drawnow limitrate
        addpoints(g,y(i),acc_z_lowpass(i));
        drawnow limitrate
        addpoints(f,z(i),gyr_y_lowpass(i));
        drawnow limitrate
        addpoints(e,w(i),acc_y_lowpass(i));
        drawnow limitrate
  end

Answer 1

[Image Analyst]

Your "frame" appears to be 3D. Using [] in imshow() doesn't work for RGB images. So you're going to have to figure out why your "frame" values are not integers in the range 0 - 255.

[Loic Van Aelst]

I'm sorry, I don't know what that means. I added the [] in imshow because I read somewhere it could help. But even by using x=[329 752]; y=[50 411]; imshow(frame(y(1):y(2),x(1):x(2),:));

It doesn't work. But the video does play when I only use imshow in the figure, without the animatedline.

[Walter Roberson]

what is max(max(max(frame(y(1):y(2),x(1):x(2),:)))) and min(min(min(frame(y(1):y(2),x(1):x(2),:))))

[Loic Van Aelst]

255 and 0

[Image Analyst]

It's not double is it? What does this say:

whos frame

Can you call imwrite and then attach it here. Step through it and when you get a black image, type this in the command window and then attach it back here with the paper clip icon

imwrite(frame, 'frame.png');

[Loic Van Aelst]

whos frame gives the following:

Name Size Bytes Class Attributes

frameA 480x854x3 1229760 uint8

[Image Analyst]

You forgot to attach it.

[Loic Van Aelst]

This is what imwrite saves

[Loic Van Aelst]

Here is a dropbox file with: https://www.dropbox.com/sh/ziw5s7pcnp8nfmu/AABNrHJxiuhPuppGT7hE9rsPa?dl=0

*A video of what happens when I put the animatedline in comment: this is what I want to have as video

• What I have now: the animatedlines work but the video is black
• my code: Parameter_extraction_for_lus_MET_DATA_SYNC_INGEBOUWD

[Image Analyst]

I can't reproduce your issue. When I display that with imshow() it looks fine, not dark or black.

[Loic Van Aelst]

yes but not when you remove the comments on the animatedline. I can't plot the animatedline and the video together. See my videos I added

[Image Analyst]

Then you will probably have to attach 'Zwemvideo1.mp4' so we can run your code completely.

[Loic Van Aelst]

Its in the dropbox file

https://www.dropbox.com/sh/ziw5s7pcnp8nfmu/AABNrHJxiuhPuppGT7hE9rsPa?dl=0

[Image Analyst]

Your code here doesn't run.

Undefined function or variable 'acc_y'.
Error in test3 (line 14)
acc_y = resample(acc_y,3,4);

Exactly what would one need to do to run it?

[Loic Van Aelst]

load('zwemproef150219.mat'); data = ['acc_x';'acc_y';'acc_z';'gyr_x';'gyr_y';'gyr_z'];

I added this zwemproef in the last link.

[Image Analyst]

Are the addpoints supposed to go to other axes, or onto the image axes?

If onto the image axes, then perhaps use hold on.

If onto one of the top 4 axes, then use subplot() to switch the current axes back to the one it's supposed to plot into.

[Loic Van Aelst]

The addpoints are supposed to go on the first 4 subplots. The 5th subplot is the video. Here is a video of the animatedline plot without the video: https://www.dropbox.com/sh/29yh6d0xw36kyw6/AABtTQugPHo5yt98a720DCtra?dl=0

Edit: I added subplot(5,1,1) and so on before the addpoints, but it doesn't chang anything