My improfile results get shorter

This might be a simple or dumb question but please help

I'm brand new to MATLAB and am trying to get intensity data out of images using improfile.

This image 'A' is a 422 X 85 image (gray scale) and I'm using the function as I1=improfile(A,[1 1],[1 422]), I2=improfile(A,[2 1],[2 422]) ...

The first I1 result gives me '422 X 1' size, but then it keeps getting shorter afterwords. (I2 - 421X1, I3 - 420X1, ...)

Am I doing something wrong?

Thanks in advance for your help.

Answer 1

[Walter Roberson]

This is expected. The number of pixels used is probably max() of delta x and delta y, with it producing one result for each integer offset in that space

[Walter Roberson]

Note that improfile sets everything up and then calls interp2 to do the work. You could construct your own profile path and call interp2 yourself if, for example, you always wanted 500 points along the path.

[Hoyong Yie]

Thank you very much.

If you could show me an example on how to construct a path it would be much appreciated.

[Walter Roberson]

N = 256;
start_at = [17 1];
end_at = [17 242];
x_path = linspace(start_at(1), end_at(1), N);
y_path = linspace(start_at(2), end_at(2), N);
I17 = interp2(double(A), x_path, y_path);

For this purpose remember that y corresponds to height, which is rows, the first index of A, and x corresponds to width, which is columns, the second index of A.

[Image Analyst]

Here is how they define the number of pixels: "improfile chooses a value for n, roughly equal to the number of pixels the path traverses."