How can I write matlab program for the following sample region selection from image?

Question

K M Ibrahim Khalilullah 2016-6-17

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/290505-how-can-i-write-matlab-program-for-the-following-sample-region-selection-from-image

评论： K M Ibrahim Khalilullah 2016-6-23

I have a point V. I have created some imaginary rays (r1,r2,r3,.....rn) from that point. How can I select two neighboring regions (like A1 and A2) on either side of the ith ray. How can I get the points of that region and the points on the ith ray? Please see the picture: In the picture r1...r3 are imaginary rays created from point V. now I need the region A1 and A2 and points on the ith ray (e.g. r2 ray) N.B. Angle between each ray is equal.

)

2 个评论
显示无隐藏无

marcel.kaszap@kin.ulaval.ca 2016-6-22

在 MATLAB Online 中打开

what about building a function that you can call whenever you need to know if a point P stands inside the wanted areas.

% 
% You know V and you know the point P that you want to know if it
% stands close to R2 (between R1 and R3)
%
% Output inside = 0 means that P is on R2
%                -1 you are outside of the areas A1 and A2
%                 1 you are inside the areas
%
function inside =tellMeWhereAmI(Vx, Vy, Px, Py, angleR2, deltaAngle)
  % what is the angle between V and P, here atan2 works between +/-Pi
  angle =atan2(Py-Vy, Px-Vx);
  % to avoid confusion around +/-Pi
  if angle < 0
    angle = 2*pi+angle;
  end
  if angleR2 < 0
    angleR2 = 2*pi+angleR2;
  end
  % to avoid confusion around 0/2Pi
  if angle <= angleR2+deltaAngle-2*pi
    angle = angle+2*pi;
  end
  % now we compare
  if angle == angleR2
    inside = 0;      % we are on the line
  elseif (angle > angleR2+deltaAngle) | (angle < angleR2-deltaAngle)
    inside = -1;     % we are outside of the areas
  else
    inside = 1;      % we are inside of the areas
  end
end

Do you think it could do the job?

MEK

K M Ibrahim Khalilullah 2016-6-23

Thanks for your answer. sorry MEK my thinking is different. I want the points between two end points of the line and the region like A1 and A2. However , I have already my work.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

marcel.kaszap@kin.ulaval.ca 2016-6-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/290505-how-can-i-write-matlab-program-for-the-following-sample-region-selection-from-image#answer_226354

在 MATLAB Online 中打开

Sorry I have forgotten a little correction, here is the final

% 
% You know V and you know the point P that you want to know if it
% stands close to R2 (between R1 and R3)
%
% Output inside = 0 means that P is on R2
%                -1 you are outside of the areas A1 and A2
%                 1 you are inside the areas
%
function inside =tellMeWhereAmI(Vx, Vy, Px, Py, angleR2, deltaAngle)
  % what is the angle between V and P, here atan2 works between +/-Pi
  angle =atan2(Py-Vy, Px-Vx);
  % to avoid confusion around +/-Pi
  if angle < 0
    angle = 2*pi+angle;
  end
  if angleR2 < 0
    angleR2 = 2*pi+angleR2;
  end
  % to avoid confusion around 0/2Pi
  if angle <= angleR2+deltaAngle-2*pi
    angle = angle+2*pi;
  elseif angle-2*pi > angleR2-deltaAngle  % I had forgotten this!!!
    angle = angle-2*pi;
  end
  % now we compare
  if angle == angleR2
    inside = 0;      % we are on the line
  elseif (angle > angleR2+deltaAngle) | (angle < angleR2-deltaAngle)
    inside = -1;     % we are outside of the areas
  else
    inside = 1;      % we are inside of the areas
  end
end