Get just the scaling transformation out of CGAffineTransform

Question

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

Answer 1

Let me propose different solution. I first rotate the affine transform in the opposite direction and just read scale from t.a and t.d:

- (CGPoint)scaleFromTransform {
    CGAffineTransform t = self.transform;
    CGFloat angle = atan2(t.b, t.a);
    // calculate rotation transform (by -angle)
    CGAffineTransform r = CGAffineTransformMakeRotation(-angle);
    // calculate main transform without rotation
    CGAffineTransform t0 = CGAffineTransformConcat(t, r);
    CGFloat xScale = t0.a;
    CGFloat yScale = t0.d;
    return CGPointMake(xScale, yScale);
}