finding x and y coordinates of the image and spline fit

I have binary image 'sceleton.tif' (black line and white background) How can I find x and y coordinates for pixels to make spline fit of the image?

Im=imread('sceleton.tif')

Answer 1

[Nitin]

if your boundary is black on the binary image, you can try the following:

[a,b]= find(Im==0);

Answer 2

[Image Analyst]

What do you mean by spline fit? Spline fit of what? The skeleton is continuous so there's nothing to interpolate, unless for some reason you want sub pixel resolution but that wouldn't make sense since the skeletonization was done with pixel resolution.

[Natalja]

You are right I have continuous pixel line and in my case I would like to have homogenous line (no pixel to pixel jumps) I am not sure if reducing pixel size will help.

Answer 3

[Leah]

You have to define the coordinate system then decide which points you want to use for interpolation. Why are you after an equation as opposed to just the (x,y) coordinates?

[Natalja]

Yes, I am after (x,y) coordinates. My goal at the end is to divide the skeleton line with many short perpendicular lines. It is a big challenge for me, cause I have never worked on MatLab before.