cairoMatrixTransformDistance: cairoMatrixTransformDistance
Description
Transforms the distance vector (dx,dy) by matrix. This is
similar to cairoMatrixTransformPoint except that the translation
components of the transformation are ignored. The calculation of
the returned vector is as follows:Usage
cairoMatrixTransformDistance(matrix, dx, dy)
Details
dx2 = dx1 * a + dy1 * c;
dy2 = dx1 * b + dy1 * d;
Affine transformations are position invariant, so the same vector
always transforms to the same vector. If (x1,y1) transforms
to (x2,y2) then (x1+dx1,y1+dy1) will transform to
(x1+dx2,y1+dy2) for all values of x1 and x2.