如何将CGRect的大小增加一定的百分比值？ [英] How can I increase the size of a CGRect by a certain percent value?

问题描述

如何将CGRect的大小增加一定的百分比值？我应该使用某种形式的 CGRectInset 来做这件事吗？

How can I increase the size of a CGRect by a certain percent value? Should I use some form of CGRectInset to do it?

示例：

假设我有一个CGRect： {10,10,110,110}

Assume I have a CGRect: {10, 10, 110, 110}

I想要将它的大小（保持相同的中心点）增加20％到：

I want to increase it's size (retaining the same center point) by 20% to:

{0,0,120,120}

推荐答案

如果您愿意，可以使用 CGRectInset ：

You can use CGRectInset if you like:

double pct = 0.2;
CGRect newRect = CGRectInset(oldRect, -CGRectGetWidth(oldRect)*pct/2, -CGRectGetHeight(oldRect)*pct/2);

要减小尺寸，请删除 - s。

To decrease the size, remove the -s.

旁注： CGRect 比<$大20％ c $ c> {10,10,100,100} 是 {0,0,120,120} 。

编辑：如果打算按面积增加，那么这样做（即使对于那些矩形也是如此） 't square）：

Edit: If the intention is to increase by area, then this'll do it (even for rectangles that aren't square):

CGFloat width = CGRectGetWidth(oldRect);
CGFloat height = CGRectGetHeight(oldRect);
double pct = 1.2; // 20% increase
double newWidth = sqrt(width * width * pct);
double newHeight = sqrt(height * height * pct);
CGRect newRect = CGRectInset(oldRect, (width-newWidth)/2, (height-newHeight)/2);

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