Perspective transform a Point not an Image

Hello,

I have four points I measured in an Image. In reality they are the corners of a rectangle.

ImagePoints = [x1 y1;x2 y2;x3 y3;x4 y4]
RealPoints = [0 0;100 0;0 60;100 60]

I measure another point lying in this rectangle. I need the real koordinates of this Point (in the rectangle).

ImageMeasurePoint = [x y]; <= I have this.
RealMeasurePoint = [x y]; <= I want this.

I don't want to transform the whole image. I just want to calculate the RealMeasurePoint. Is there a function I can use?

Can you help me.

Thanks Timo

Answer 1

[Teja Muppirala]

If you have the Image Processing Toolbox, using cp2tform and tformfwd makes this very easy, and will work even when ImagePoints is not a perfectly straight rectangle:

ImagePoints = [10 10; 110 10; 10 310; 110 310];
RealPoints = [0 0;100 0;0 60;100 60]; 
T = cp2tform(ImagePoints,RealPoints,'projective')

ImageMeasurePoint = [60 160];

RealMeasurePoint = tformfwd(T,ImageMeasurePoint)

Answer 2

[Timo]

Hall Teja!

Your my hero! Thanks a lot! Thumbs up! I'm happy now!

Wish you a nice day! You deserve it.

Thanks Timo