Question

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？

示例：

假设我有一个CGRect：{10, 10, 110, 110}

我希望将它的大小（保留相同的中心点）增加20％：

{0, 0, 120, 120}

Answer 1

如果您愿意，可以使用CGRectInset：

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

要缩小尺寸，请移除-。

旁注：比CGRect大20％的{10, 10, 100, 100}为{0, 0, 120, 120}。

编辑：如果打算按区域增加，那么这样做（即使对于不是方形的矩形）：

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);

Answer 2

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

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

Answer 3

当然，使用CGRectInset有效：

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

Answer 4

使用Swift，您可以保留中心点（相对于源Rect）并使用扩展名增加/减小大小，如下所示：

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)

Answer 5

我在我的Swift代码中使用CGRect> insetBy

Demo

以此为例，您的百分比值为scaleX。

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

使用正值缩小比例
使用负值放大

Answer 6

Swift 4扩展程序通过简化的计算受到以下几个答案的启发：

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)
    }
}

用法很简单：

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

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))
    }
}

Answer 7

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

~~请注意，此方法也会更改矩形的x和y。~~

如何将CGRect的大小增加一定的百分比值？

7 个答案: