# can I equation of a curve from an image?

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Is it possible to find the equation of a curve from an image?

I want to find the equation of the line in green:

##### 3 Comments

Matt J
on 25 Apr 2022

### Answers (1)

Matt J
on 25 Apr 2022

Edited: Matt J
on 25 Apr 2022

This assumes your Image is already cast to type logical. The slope and intercept are for the center-line in matrix (row,column) coordinates.

reg=regionprops(Image,'PixelList');

x1=reg(1).PixelList(:,2);

y1=reg(1).PixelList(:,1);

x2=reg(2).PixelList(:,2);

y2=reg(2).PixelList(:,1);

A=[x1,x1.^0,0*x1;

x2,0*x2,x2.^0];

b=[y1;y2];

c=A\y;

slope=c(1);

intercept=mean(c(2:3));

##### 7 Comments

Matt J
on 25 Apr 2022

Edited: Matt J
on 25 Apr 2022

I identify the lines by the camera and then create the green line in the middle of the lines. I want to find the green line equation. Here is the code for finding the green line:

If you already have the points on the green line, what prevents you from using fit(), lsqcurvefit(), or similar? Also, you have articulated that you want to model this as a polynomial, but of what order? Are you sure you don't need a piecewise polynomial? In any case, fit() offers all of these.

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