About "projective" command

I have a problem, i have an imagen and then i applied "imtransform" like this tutorial ( http://www.mathworks.com/help/toolbox/images/ref/imtransform.html). I used tform = maketform('projective'...). So the question: Is there anyway to known where goes any pixel and known what is it his transformation in the new coordinates?. I hope you can help me

Thanks.

Alex

Answer 1

[Alex Taylor]

Yes,

The functions tformfwd and tforminv are what you are looking for.

help tformfwd
help tforminv

You can calculate where the forward transformation T maps in the input point (1,2) using the following example:

    tform = maketform('projective',[2 1 0; 2 1 2; 0.1 0 2]);
    [X,Y] = tformfwd(tform,1,2)

Hope that helps,

Alex.

[Alex Molina]

Thanks a lot Alex, it´s works perfectly

[Yanliang]

Hey Alex,

I am doing imtransform, yet it scale the output image automatically,

And I can not find the destination of a specific feature point.

Could you help me out?

Related codes for checking:

[ imgDouble{1}, ybound, xbound ] = imtransform( imgDouble{1}, tform );

Ap = tformfwd( tform, inlier_array );
Ap = mean(Ap);
ApCord = tformfwd( tform, [ [1, 1]; [height, 1]; [1, width]; [height, width] ] );
ApCord = [ min( ApCord ); max( ApCord ) ];
AppH = xbound(2) - xbound(1) + 1;
ApCordH = ApCord( 2, 1 ) - ApCord( 1, 1 ) + 1;
App(1) = ( Ap(1) - ApCord( 1, 1 ) + 1 ) * AppH / ApCordH + xbound(1) - 1;
AppW = ybound(2) - ybound(1) + 1;
ApCordW = ApCord( 2, 2 ) - ApCord( 1, 2 ) + 1;
App(2) = ( Ap(2) - ApCord( 1, 2 ) + 1 ) * AppW / ApCordW + ybound(1) - 1;
B_Location = mean( dest_array );
A_Location = App - [ xbound(1), ybound(1) ] + [1, 1];
offset_AB = A_Location - B_Location + [1, 1];
putative_off_B = offset_AB ;