How to calculate coordinates for angled view of surface??
Tom Benson  [5 posts]
10 years
Hello all,

I have what I think should be a simple problem...except I'm not handy with Trigonometry.

I'm taking a photo of a tabletop from about 12" above it, not directly above but from the corner.  Imagine a camera hovering 12 inches above the right hand corner of a kitchen table, pointing down.

I know the angle of the camera reletive to the tabletop.  I want to be able to look at the photo and from the X,Y location on the photo, interpolate the X,Y, and Z location in real life.

Does anybody know the formulas for converting x,Y locations on a JPEG into X,Y,Z coordinates?  Is there a good website or book that has details on this sorta thing?

Thanks for any advice,

Anonymous 10 years
See attached link


Tom Benson  [5 posts] 10 years
Here is a photo...

Took an 11 inch piece of paper and marked 0, 11, and 5 1/2 inch marks.

The photo was taken from a camera 7 inches vertical above the plane of the paper, and 51/2 inches "behind" the paper (behind the 0 mark).

I'm looking for a piece of software or macro or set of formulas which will automatically estimate the X.Y coordinates of any given "dot" on that white paper, reletive to the edges of the paper itself, by reading and translating the X,y coordinates in a 640X480 snapshot.  This will need to take into account:

- the size of the photo
- perspective distortion of coordinates
- the angle of the camera reletive to the plane.

I'm not going to try develop such a formula myself from scratch starting with Trig...that would be a waste of time.  I'm sure it exists in a zillion different places, and I don't mind paying for it.  But don't know which search terms to use to find it.

Camera transform
10 years
I believe this is called a -camera transform-.  Don't have any links but this function is used all over the 3-D graphics world...good luck
10 years
there is a function in roborealm for that! its in th transforms subfolder an is called affine. how to use it: drag the squares over the corners of you tabletop this will cause the tabletop to apear straight
Anonymous 10 years
almost forgot the robo file :P

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