blocks|key|312685|text|假设转换是缩放，然后是旋转(可能有平移，但没有倾斜)，水平缩放因子是sqrt(a%5E2%2Bc%5E2)，垂直缩放因子是sqrt(b%5E2%2Bd%5E2)，水平缩放因子与垂直缩放因子的比率应该是a/d+=+-c/b，其中a、b、c和d是CGAffineTransform的六个成员中的四个，每个代码(<+the+documentation+>D9和<代码>D10只表示平移，这不会影响缩放因子)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|312686|%7C++a++b+0+%7C
%7C++c++d+0+%7C
%7C+tx+ty+1+%7C|code-block|syntax|javascript|312687|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.apple.com/reference/coregraphics/cgaffinetransform^0|Y|D|1J|D|2G|A|2T|1|2V|1|2X|1|2Z|1|31|H|3Z|H|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@$9|19|A|1A|1|1B]]|E|$]]|$1|F|3|G|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

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 <code>sqrt(a^2+c^2)</code>, the vertical scale factor is <code>sqrt(b^2+d^2)</code>, and the ratio of the horizontal scale factor to the vertical scale factor should be <code>a/d = -c/b</code>, where <code>a</code>, <code>b</code>, <code>c</code>, and <code>d</code> are four of the six members of the <code>CGAffineTransform</code>, per <a href="https://developer.apple.com/reference/coregraphics/cgaffinetransform" rel="noreferrer">the documentation</a> (<code>tx</code> and <code>ty</code> only represent translation, which does not affect the scale factors).

<pre><code>| a b 0 |
| c d 0 |
| tx ty 1 |
</code></pre>

blocks|key|307587|text|这是一个老问题，但我仍然添加了更多的信息，以防有人需要。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|307588|对我来说，获取缩放、旋转变换和重现变换的好答案和示例代码来自文章：|307589|http://www.informit.com/articles/article.aspx?p=1951182|offset|length|307590|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|1J|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@$F|R|G|S|1|T]]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|E]]]]

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:

<a href="http://www.informit.com/articles/article.aspx?p=1951182" rel="noreferrer">http://www.informit.com/articles/article.aspx?p=1951182</a>

blocks|key|3261900|text|-+(CGFloat)xscale+{
++++CGAffineTransform+t+=+self.transform;
++++return+sqrt(t.a+*+t.a+%2B+t.c+*+t.c);
}

-+(CGFloat)yscale+{
++++CGAffineTransform+t+=+self.transform;
++++return+sqrt(t.b+*+t.b+%2B+t.d+*+t.d);
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3261901|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>- (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);
}
</code></pre>

blocks|key|3261916|text|这是一个老问题(在Swift之前)，所以对于Swift的人来说，基于对CGAffineTransform的搜索，这是一个基于其他答案的Swift+3便利扩展：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3261917|extension+CGAffineTransform+{
++++var+xScale:+CGFloat+{+return+sqrt(self.a+*+self.a+%2B+self.c+*+self.c)+}
++++var+yScale:+CGFloat+{+return+sqrt(self.b+*+self.b+%2B+self.d+*+self.d)+}
++++var+rotation:+CGFloat+{+return+CGFloat(atan2(Double(self.b),+Double(self.a)))+}
++++//+.tx+and+.ty+are+already+available+in+the+transform+
}|code-block|syntax|javascript|3261918|编辑:更新了旋转，根据评论使用替身。谢谢！|3261919|entityMap^0|Z|H|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

It's an old (pre-Swift) question so for Swift folk arriving here based on a search for <code>CGAffineTransform</code> here's a Swift 3 convenience extension based on the other answers:

<pre><code>extension CGAffineTransform {
 var xScale: CGFloat { return sqrt(self.a * self.a + self.c * self.c) }
 var yScale: CGFloat { return sqrt(self.b * self.b + self.d * self.d) }
 var rotation: CGFloat { return CGFloat(atan2(Double(self.b), Double(self.a))) }
 // .tx and .ty are already available in the transform 
}
</code></pre>

[Edit: Updated rotation to use Doubles in light of the comment. Thx!]

blocks|key|3048260|text|让我提出不同的解决方案。我首先将仿射变换旋转到相反的方向，然后从t.a和T.D读取scale：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3048261|-+(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);
}|code-block|syntax|javascript|3048262|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

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:

<pre><code>- (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);
}
</code></pre>

blocks|key|310601|text|Swift+4扩展(感谢Robin+Macharg的回答)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|310602|extension+CGAffineTransform
{
++++var+xScale:+CGFloat+{+return+sqrt(a+*+a+%2B+c+*+c)+}
++++var+yScale:+CGFloat+{+return+sqrt(b+*+b+%2B+d+*+d)+}
++++var+rotation:+CGFloat+{+return+CGFloat(atan2(Double(b),+Double(a)))+}
++++var+xOffset:+CGFloat+{+return+tx+}
++++var+yOffset:+CGFloat+{+return+ty+}
}|code-block|syntax|javascript|310603|请注意，在大多数平台上，CGFloat等于Double，因此转换需要为Double。|310604|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Swift 4 Extension (thanks to Robin Macharg's answer)

<pre><code>extension CGAffineTransform
{
 var xScale: CGFloat { return sqrt(a * a + c * c) }
 var yScale: CGFloat { return sqrt(b * b + d * d) }
 var rotation: CGFloat { return CGFloat(atan2(Double(b), Double(a))) }
 var xOffset: CGFloat { return tx }
 var yOffset: CGFloat { return ty }
}
</code></pre>

Note that CGFloat equals a Double on most platforms, thus conversions need to be to Double.

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)

Get just the scaling transformation out of CGAffineTransform

Swift

我发现了一个关于仅获得旋转的类似问题，但据我所知，缩放和旋转在变换矩阵中的工作方式不同。矩阵不是我的强项，所以如果有人能提示我如何从CGAffineTransform中获得伸缩，我将不胜感激。顺便说一句。我尝试在CGSize上应用CGAffineTransform，然后获取height x width来查看它缩放了多少...

问仅获取CGAffineTransform的缩放转换
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