Counting pixel at an angle without rotating image

How to count the pixels along the line (red) that is perpendicular to the major axis (blue) of a region, without rotating the image?

Answer 1

[Image Analyst]

You know the centroid (xCentroid, yCentroid), and you know the slope (because you drew the line). The perpendicular slope is -1/mainSlope. The equation of a line is (y-y0) = slope * (x-x0). Or

perpSlope = -1 / mainSlope;
y = perpSlope * (x - x0) + y0;

Put in (x0,y0) of the point you want to take the cross section of - the point along the main slope. Then put in x = 1, for the left edge, and x = (number of columns in the image) for the right edge. That will get you two endpoints of the line. Then just call improfile() to get a line drawn across, and use find() to determine the x and y locations of where the line crosses the white region.

[Hg]

This works! Image Analyst, thanks for being a great help!

[Image Analyst]

You're welcome. I'm glad you were able to get it working with just the few steps that I outlined. And thanks for Accepting the answer.