select

Read an image into the MATLAB® workspace.

I = imread("cameraman.tif");

Define the helperGetSubsetOfPoints function, which detects and selects SURF points. You must save the helper function as a MATLAB script file with a .m extension.

function indexedLocation = helperGetSubsetOfPoints(I)
    points = detectSURFFeatures(I);
    indexedPoints = select(points,30:100);
    indexedLocation = indexedPoints.Location;
end

Create a configuration object for generating a MEX function.

cfg = coder.config("mex");

Generate the MEX function from the helper function helperGetSubsetOfPoints using the configuration cfg. The helperGetSubsetOfPoints function detects SURF features in the input image and selects a specified set of point features using the select object function of the SURFPoints object. The helperGetSubsetOfPoints function outputs the locations of the selected SURF point features in the image. You can use the select function only for code generation.

codegen -config cfg helperGetSubsetOfPoints -args {I}

Code generation successful.

Call the generated MEX function with the image I as input. Because code generation cannot return objects as outputs, the helperGetSubsetOfPoints function outputs the locations of the selected SURF point features.

locations = helperGetSubsetOfPoints_mex(I);

Convert the output locations to SURFPoints objects.

points = SURFPoints(locations);

Display the selected SURF point features.

figure
imshow(I)
hold on
plot(points)

hold off