MATLAB Answers

MMSAAH
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How can I find maximums in the intensity profile and display it in the original image ?

Asked by MMSAAH
on 13 Sep 2019
Latest activity Commented on by darova
on 17 Sep 2019 at 18:14
I have ('liftingbody.png') image and I want to display the intensity profile along a white curve ('sss.png').
I searched the coordinates of the white curve and I displayed the intensity profile of the ('liftingbody.png') along those coordinates.
After that, I searched the maximums in the c profile and I displayed it in the fused image.
My problem is why I got points outside the red curve ? here is my code.
Could anyone help me solving this problem ?
clear all, close all; clc
I2 = imread('liftingbody.png');
figure
imshow(I2);
I=imread('sss.png');
figure
imshow(I);
[x2,y2]=find (I>0); % find the coordinates of white line
[cx,cy,c]=improfile(I2, x2,y2); % display the intensity profile.(cx,xy):coordinates of intensity profile
% [pks,locs] = findpeaks(c);
[pks,locs] = findpeaks(c,'MinPeakDistance',50); % search maximums
figure
plot(c)
% display the curve in red
I = uint8(I);
[x,y,z]=size(I);
for i=1:x
for j=1:y
if (I(i,j)==1)
I(i,j,1)=255;
I(i,j,2)=0;
I(i,j,3)=0;
end
end
end
figure
imshow(I);
title('red curve');
I = imfuse(I, I2,'blend','Scaling','joint');
figure
imshow(I);
hold on
plot(cy(locs(:)),cx(locs(:)),'b*')

  5 Comments

I want to find the max in the intensity profile and display it in the original image.
sss.png image provide as the x2,y2 coordinates on which the intensity profile could be dispayed.
Here attached you could fing the liftingbody.png image
thank you for your answer but if you zoom in the picture even more, you will see many points outside the red curve.

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3 Answers

Answer by darova
on 16 Sep 2019 at 17:33
 Accepted Answer

I think the problem is in order of points. MAthworks help:
improfile
Pixel-value cross-sections along line segments
Try this
I=imread('sss.png');
[x2,y2] = find (I>0); % find the coordinates of white line
figure
imshow(I);
hold on
for i = 1:10:length(x2)
plot(y2(i),x2(i),'.r')
pause(0.1)
end
hold off
And now add this before plot()
[x2 ,ix] = sort(x2); % sort vertically
y2 = y2(ix);
So i divided white line into two parts. Sorted top part vertically and bottom part horizontally
See attached script

  2 Comments

Thank you very much. This did solve my problem. I'm really grateful.
The problem was in fact related to the order of points
Could you explain me more please ? How did the sort () command solve the problem ?
Thanks a lot.
Imagine you have six pixels. You want to find (rows,columns) (position) of them
So order of pixels would be as i marked on the picture
111Untitled.png
Arrows indicate direction of search
So when you have some curve (marked black) and points (red) you have to find improfile
Blue lines will be the actual path of profile
12Untitled.png

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Answer by KALYAN ACHARJYA on 13 Sep 2019
Edited by KALYAN ACHARJYA on 13 Sep 2019

My problem is why I got points outside the red curve ? here is my code?
scatter(cy(locs(:)),cx(locs(:)),'b')
I dot think there are any points positioning the outside the Marker line (white line turned red line), use other plot way and see the results.
345.png

  3 Comments

thank you for your answer but if you zoom in the picture even more, you will see many points outside the red curve even when changing plot by scatter
May be there are few white pixels, just near the boundary. When I executed the code, all points are lie on the white line (as showed result)...again trying to visulize the plot.
zoomed_image.JPG
Here is the image zoomed. Many points are outside the red curve.

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Answer by MMSAAH
on 16 Sep 2019 at 15:27

The problem still exists.
Could anyone help me solving this issue please.

  0 Comments

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