I have a set of (x,y) coordinates that enclose a irregular shape, I want to extract all the points that are inside that particular region. How should i approach this.

Basically I have an image in which I have marked certain regions, I want to know about all the points inside that region.

Answer 1

[Walter Roberson]

There are an infinite number of points inside any non-degenerate polygon (for degenerate polygons, you need to define "inside" with some care to boundary conditions.)

If you are asking about matrix coordinates then poly2mask() and then if you want you can extra the content of the matrix according to the mask.

[Aditya]

Thanks for the help. Ill look into it.

Answer 2

[Image Analyst]

If you want the pixel values, then you can do

mask = poly2mask(x, y, rows, columns);
pixelValues = grayImage(mask);

If you want other things, like the area of the shape, then see my Image Processing Tutorial http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862