I want to use detectSURFFeatures function and get the result in the form of coordinates x,y ?

How can I get the result of detectSURFFeatures in the form of (x1,Y1, x2,y2,.......),ie in coordinates form. can any one help me thank you in advance

Answer 1

[Walter Roberson]

https://www.mathworks.com/help/vision/ref/surfpoints-class.html

points = detectSURFFeatures(I);
xxyy = points.Location;
xyxy = reshape( xxyy.', 1, []);

That is, xxyy is an M x 2 array in which the x are the first column and the y are the second column. But you want a row vector in which the x and y alternate, so it is necessary to transform the 2D array to get the vector you want. (Personally I think the 2D array is a lot easier to work with...)

[George Ibrahim]

Thank you for responding but I still have a problem

I use the following code:

I = imread('A.png');
texture = rgb2gray(I);
points = detectSURFFeatures(texture);
points = (points.selectStrongest(6));
xxyy = points.Location;
xyxy = reshape( xxyy.', 1, []);
xyxy = pts_2D;
pts_3D=zeros(size(pts_2D,1),3);
for j=1:size(pts_2D,1)
    pts_3D(j,:)=unproject(pts_2D(j,2),pts_2D(j,1),1:3);
end;

the for loop does not accept input in the form of [x1 y1 x2 y2 ....] it accepted the input when I set it manually [x1,y1; x2,y2; ....] where x's and y's are integers (does not accept fractions) so how can I reach to this form by commands

I'm sorry I'm new to Matlab, I'd be grateful if you can help me further more

Thank you in advance.

[Walter Roberson]

unproject is not a Mathworks-provided command, and it also is not part of any File Exchange contribution.

You overwrite your calculated data with the undefined pts_2D .

I speculate you want this:

I = imread('A.png');
texture = rgb2gray(I);
points = detectSURFFeatures(texture);
Nfeat = 6;
points = (points.selectStrongest(Nfeat));
xxyy = round( points.Location );
pts_3D = zeros(Nfeat, 2, size(I,3), class(I));
for j = 1 : Nfeat
  pts_3d(j, :) = I(xxyy(j, 1), xxyy(j,2), :);
end

[George Ibrahim]

You are right unproject is not Matlab command but it belongs to external toolbox and libraries(Rendrer&Open seen graph I tried the code you sent but it gave me the same error Index exceeds matrix dimensions.

Error in WalterRoberson (line 9) pts_3d(j, :) = I(xxyy(j, 1), xxyy(j,2), :); do you have any suggestions Thank you

[Walter Roberson]

Try

for j = 1 : Nfeat
  pts_3d(j, :) = I(xxyy(j, 2), xxyy(j, 1), :);
end

[George Ibrahim]

yes this works ok Thank you very much