I found a similar question about getting just the rotation, but as I understand scaling and rotating work different in the transform matrix.
Matrixes are not my strength, so if anybody would hint me how to get only the scaling out of a CGAffineTransform I'd greatly appreciate.
btw. I tried applying the CGAffineTransform on a CGSize and then get the height x width to see how much it scaled, but height x width have strange values (depending on the rotation found in the CGAffineTransform, so ... hm that does not work)
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 |
- (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); }
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