How can I get estimated coordinates after performing transformation?

I have a set of 15 matched points as below.

base_points= [202.5 198.5; 3998.5 198.5; 4002.5 2602.5; 202.5 2602.5; 1002.5 198.5; 3202.5 198.5; 3202.5 2602.5; 1002.5 2602.5; 1802.5 198.5; 2402.5 198.5; 2402.5 2602.5; 1802.5 2602.5; 202.5 802.5; 4002.5 802.5; 4002.5 2002.5];

input_points= [278.5 246.5; 4038.5 170.5; 4162.5 2702.5; 170.5 2622.5; 994.5 194.5; 3250.5 146.5; 3322.5 2730.5; 922.5 2678.5; 1790.5 154.5; 2414.5 138.5; 2430.5 2738.5; 1766.5 2722.5; 226.5 810.5; 4102.5 766.5; 4162.5 2050.5];

I would like to perform 2 types of transformations, one with 2nd order polynomial and another one with piecewise linear transformation. I am using cp2tfrom as shown below.

t_poly_ord2 = cp2tform(input_points, base_points,'polynomial',2);

t_piecewise_l = cp2tform(input_points, base_points,'piecewise linear');

Is there any way to get the estimated coordinates of the both transformations?

Answer 1

[Matt Fig]

Have you looked at TFORMFWD?

[Liew]

Yes, I have tried but same error prompted when I run as below.

estm_poly2 = tformfwd(t_poly_ord2, input_points);

estm_pwl = tformfwd(t_piecewise_l, input_points);

Error displayed:

??? Error using ==> tform>checkTform at 109 Function TFORMFWD expected T's forward_fcn field to be non-empty.

Error in ==> tform at 30 [t, A] = checkTform(f, numout, varargin{:});

Error in ==> tformfwd at 68 varargout = tform('fwd', nargout, varargin{:});

I checked the tform struct of the both transformations and found out that both forward_fcn are empty. Anything I did it wrongly? However, I still can get the transformed images if I perform imtransfrom like this:

imtrans_poly2 = imtransform(I_input,t_poly_ord2,... 'XData',[1 info.Width], 'YData',[1 info.Height]);

imtrans_pwl = imtransform(I_input,t_piecewise_l,... 'XData',[1 info.Width], 'YData',[1 info.Height]);

Is it correct if I use fliptform to convert inverse_fcn into forward_fcn as shown below?

ft_poly_ord2 = fliptform(t_poly_ord2);

ft_pwl = fliptform(t_piecewise_l);

[Liew]

I have tried to use fliptform to convert inverse_fcn into forward_fcn and then use tformfwd. The coordinates are not correct, not match with the points' position on the image after transformed.