Get just the scaling transformation out of CGAffineTransform
- (CGFloat)xscale {
CGAffineTransform t = self.transform;
return sqrt(t.a * t.a + t.c * t.c);
}
- (CGFloat)yscale {
CGAffineTransform t = self.transform;
return sqrt(t.b * t.b + t.d * t.d);
}
That is an old question, but I still add more information in case someone needs.
For me, the good answer and sample code for getting scale, rotation of transformation and for reproducing it are from article:
http://www.informit.com/articles/article.aspx?p=1951182
Assuming that the transformation is a scaling followed by a rotation (possibly with a translation in there, but no skewing) the horizontal scale factor is sqrt(a^2+c^2)
, the vertical scale factor is sqrt(b^2+d^2)
, and the ratio of the horizontal scale factor to the vertical scale factor should be a/d = -c/b
, where a
, b
, c
, and d
are four of the six members of the CGAffineTransform
, per the documentation (tx
and ty
only represent translation, which does not affect the scale factors).
| a b 0 |
| c d 0 |
| tx ty 1 |