Automatically measure the major axis of image and ortogonal axis

Hello everyone. I need help for automatically measure the major axis of image and after to measure the perpendicular major axis. In image the Region of Interest (ROI) is the set of white pixels. Actually i have this steps in my tool:

1. I select two points (of extreme the supposed major axis)
2. I measure in milimeters this length and draw a line
3. I draw perpendicular lines along the line of major axis
4. I select one of this line, that represents the major perpendicular axis of region.

I put the image of example that i have to ilustrate da region.

If anyone help me with this resolution, i thank you.

Answer 1

[Image Analyst]

See my attached program. It finds the two farthest points on a blob, and finds the cross section at the midpoint also.

[Duarte Gonçalves]

Hi Image Analyst. I thank you for your rapidly response. I'm not answered to you befor because i need to experiment many images and testing my code. It was the only reason. Your hint not help me totally. I need to measure the 2 major ortogonal axes of ROI (only the region with white pixels). The measurement is necessary about white pixels, so can't have also black pixels. I put 2 images for ilustrate the ROI and the aim of my measurements.

In this image interesting me that the second axes is ortogonal to pink axe (therefore two axes will be in white pixels region of ROI).

I thank you for your code hints! Best regards.