MATLAB: How to visualize MajorAxisLength and MinorAxisLength on images

image processingImage Processing Toolboxmajoraxislengthminoraxislength;orientationregionprops

Hi,

I would like to replicate something similar to that shown in the explanation of "Orientation" property of the "regionprops" function, as viewable here:

http://it.mathworks.com/help/images/ref/regionprops.html

I would plot the red ellipse and the blue lines representing the axes, over my images (both binary and grayscale). I found this example:

http://blogs.mathworks.com/steve/2010/07/30/visualizing-regionprops-ellipse-measurements/

but I can't understand how complete the code to plot the blue lines. Could anyone help me, please?

Thanks for your answers.

Best Answer

Get the two endpoints of the line, then call plot. For example x1 = xCentroid + (majorAxisLength/2) * cosd(orientation). Same for y1, x2,and y2. It's just simple trigonometry. Then call plot([x1,x2], [y1,y2], 'r-').

Related Solutions

MATLAB: Is MinorAxisLength always perpendicular to the MajorAxisLength

The lengths itself are not perpendicular to anything, because they are scalars. The replied lengths are:

 'MajorAxisLength' Length (in pixels) of the major axis of the ellipse that has the same
 normalized second central moments as the region
 (equivalent for "Minor")

The major and minor axes of an ellipse (not their lengths) are perpendicular by definition.

MATLAB: How to draw a line along the major axis as found with regionprops

If you get the Centroid and Orientation and MajorAxisLength properties, then this becomes mostly a traditional y = m*x + b problem, where m is tan() of the Orientation and b is chosen so that the line passes through the Centroid.

Or even easier, MajorAxisLength * cosd(Orientation) to get the x axis coordinate difference, center that around the Centroid, likewise MajorAxisLength * sind(Orientation) to get the y coordinate difference, center that around the Centroid; then line() between the two endpoints.

Best Answer

Related Solutions

MATLAB: Is MinorAxisLength always perpendicular to the MajorAxisLength

MATLAB: How to draw a line along the major axis as found with regionprops

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