ios 如何将 CGRect 的大小增加某个百分比值？

How can I increase the size of a CGRect by a certain percent value?

提问by brandonscript

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

如何将 CGRect 的大小增加某个百分比值？我应该使用某种形式的CGRectInset吗？

Example:

例子：

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

假设我有一个 CGRect： {10, 10, 110, 110}

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

我想将它的大小（保留相同的中心点）增加 20% 到：

{0, 0, 120, 120}

{0, 0, 120, 120}

回答by Ian MacDonald

You can use CGRectInsetif you like:

CGRectInset如果您愿意，可以使用：

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

To decrease the size, remove the -s.

要减小大小，请删除-s。

Side note: A CGRectthat is 20% bigger than {10, 10, 100, 100}is {0, 0, 120, 120}.

附注：一个CGRect是比大20％{10, 10, 100, 100}的{0, 0, 120, 120}。

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

编辑：如果打算按面积增加，那么这样做（即使对于不是正方形的矩形）：

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);

回答by Logan

In Swift:

在斯威夫特：

func increaseRect(rect: CGRect, byPercentage percentage: CGFloat) -> CGRect {
    let startWidth = CGRectGetWidth(rect)
    let startHeight = CGRectGetHeight(rect)
    let adjustmentWidth = (startWidth * percentage) / 2.0
    let adjustmentHeight = (startHeight * percentage) / 2.0
    return CGRectInset(rect, -adjustmentWidth, -adjustmentHeight)
}

let rect = CGRectMake(0, 0, 10, 10)
let adjusted = increaseRect(rect, byPercentage: 0.1)
// -0.5, -0.5, 11, 11

In ObjC:

在 ObjC 中：

- (CGRect)increaseRect:(CGRect)rect byPercentage:(CGFloat)percentage
{
    CGFloat startWidth = CGRectGetWidth(rect);
    CGFloat startHeight = CGRectGetHeight(rect);
    CGFloat adjustmentWidth = (startWidth * percentage) / 2.0;
    CGFloat adjustmentHeight = (startHeight * percentage) / 2.0;
    return CGRectInset(rect, -adjustmentWidth, -adjustmentHeight);
}

CGRect rect = CGRectMake(0,0,10,10);
CGRect adjusted = [self increaseRect:rect byPercentage:0.1];
// -0.5, -0.5, 11, 11

回答by rmaddy

Sure, using CGRectInsetworks:

当然，使用CGRectInset作品：

CGRect someRect = CGRectMake(10, 10, 100, 100);
someRect = CGRectInset(someRect, someRect.size.width * -0.2, someRect.size.height * -0.2);

回答by gheclipse

Swift 4 extension inspired by several of the answers here with simplified calculations:

Swift 4 扩展受到这里的几个答案的启发，并进行了简化计算：

extension CGRect {
    func scaleLinear(amount: Double) -> CGRect {
        guard amount != 1.0, amount > 0.0 else { return self }
        let ratio = ((1.0 - amount) / 2.0).cgFloat
        return insetBy(dx: width * ratio, dy: height * ratio)
    }

    func scaleArea(amount: Double) -> CGRect {
        return scaleLinear(percent: sqrt(amount))
    }

    func scaleLinear(percent: Double) -> CGRect {
        return scaleLinear(amount: percent / 100)
    }

    func scaleArea(percent: Double) -> CGRect {
        return scaleArea(amount: percent / 100)
    }
}

Usage is simply:

用法很简单：

rect.scaleLinear(percent: 120.0)  OR (amount: 1.2)
rect.scaleArea(percent: 120.0)  OR (amount: 1.2)

If you are interested in trying my testing methods:

如果您有兴趣尝试我的测试方法：

/// Testing
extension CGRect {
    var area: CGFloat { return width * height }
    var center: CGPoint { return CGPoint(x: origin.x + width/2, y: origin.y + height/2)
    }

    func compare(_ r: CGRect) {
        let centered = center.x == r.center.x && center.y == r.center.y
        print("linear = \(r.width / width), area = \(r.area / area) centered \(centered)")
    }

    static func ScaleTest() {
        let rect = CGRect(x: 17, y: 24, width: 200, height: 100)
        let percent = 122.6
        rect.compare(rect.scaleLinear(percent: percent))
        rect.compare(rect.scaleArea(percent: percent))
    }
}

回答by ihsanberahim

I'm using CGRect > insetBy in my Swift code

我在我的 Swift 代码中使用 CGRect > insetBy

https://developer.apple.com/documentation/coregraphics/cgrect/1454218-insetby

https://developer.apple.com/documentation/coregraphics/cgrect/1454218-insetby

With this, your percent value will be the scaleXas my example.

有了这个，您的百分比值将scaleX作为我的示例。

    let dx = rectWidth*scaleX
    let dy = rectHeight*scaleX
    let rectangle = CGRect(x: rectX,
                           y: rectY,
                           width: rectWidth,
                           height: rectHeight).insetBy(dx: -dx, dy: -dy)

• use positive value to scale down
• use negative value to scale up

• 使用正值缩小
• 使用负值放大

回答by Nick

Using Swift you can retain the center point (relative to the source Rect) and increase/decrease the size as follows using an extension:

使用 Swift，您可以保留中心点（相对于源 Rect）并使用扩展如下增加/减少大小：

extension CGRect {
    func centerAndAdjustPercentage(percentage p: CGFloat) -> CGRect {
        let x = self.origin.x
        let y = self.origin.y
        let w = self.width
        let h = self.height

        let newW = w * p
        let newH = h * p
        let newX = (w - newW) / 2
        let newY = (h - newH) / 2

        return CGRect(x: newX, y: newY, width: newW, height: newH)
    }
}
let newRect = oldRect.centerAndAdjustPercentage(percentage: 0.25)

回答by Taras

let scale = percent / 100
let newRect = oldRect.applying(CGAffineTransform(scaleX: scale, y: scale))

Beware that this approach also will change x and y of rectangle.

请注意，这种方法也会改变矩形的 x 和 y。