Re: Problem with perspective transform matrix

Willem Vervuurt <willem@xxxxxxx> · Tue, 29 May 2007 16:52:26 +0200

Hi David,

thanks for your input. I have already tried that, but it is not the
case. Your suggestion is equal to using exactly my method but with an
inverted transformation matrix (I have implemented this to make sure,
see http://www.rodo.nl/error_inv.jpg
for the output generated after
switching source <--> destination).

Something more complicated must be going on...

Regards,

Willem

David Hodson wrote:

  Hi Willem,

    However, when I use this transformation matrix in my own code, I get 
strange results, even using the function gimp_matrix3_transform_point 
from gimpmatrix.c.

It looks like you are applying the transform in the wrong direction...

    To compute a transformed coordinate (x', y') I simply multiply 
(x, y, 1) by the transformation matrix that GIMP shows

In that case, I think that the transformation converts the destination 
coordinate to the corresponding source coordinate.

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