19

比如说，我有两个 CGRect，CGRect A 和 CGRect B。我的 UIView 的帧与 CGRect B 相同，但我想创建一个动画来显示 UIView 从帧 A 过渡到 B。

我试图通过更改 UIView 的转换属性来做到这一点，所以我不必过多地弄乱它的框架。但是，我需要 CGAffineTransform 来实现这一点。计算这种变换的最佳方法是什么？

4

6 回答 6

43

以前的答案对我不起作用。这应该有效：

斯威夫特 5（扩展）

extension CGAffineTransform {
    init(from source: CGRect, to destination: CGRect) {
        let t = CGAffineTransform.identity
            .translatedBy(x: destination.midX - source.midX, y: destination.midY - source.midY)
            .scaledBy(x: destination.width / source.width, y: destination.height / source.height)
        self.init(a: t.a, b: t.b, c: t.c, d: t.d, tx: t.tx, ty: t.ty)
    }
}

斯威夫特 4

func transformFromRect(from source: CGRect, toRect destination: CGRect) -> CGAffineTransform {
    return CGAffineTransform.identity
        .translatedBy(x: destination.midX - source.midX, y: destination.midY - source.midY)
        .scaledBy(x: destination.width / source.width, y: destination.height / source.height)
}

迅速

func transformFromRect(from: CGRect, toRect to: CGRect) -> CGAffineTransform {
    let transform = CGAffineTransformMakeTranslation(CGRectGetMidX(to)-CGRectGetMidX(from), CGRectGetMidY(to)-CGRectGetMidY(from))
    return CGAffineTransformScale(transform, to.width/from.width, to.height/from.height)
}

Objective-C

+ (CGAffineTransform) transformFromRect:(CGRect)sourceRect toRect:(CGRect)finalRect {
    CGAffineTransform transform = CGAffineTransformIdentity;
    transform = CGAffineTransformTranslate(transform, -(CGRectGetMidX(sourceRect)-CGRectGetMidX(finalRect)), -(CGRectGetMidY(sourceRect)-CGRectGetMidY(finalRect)));
    transform = CGAffineTransformScale(transform, finalRect.size.width/sourceRect.size.width, finalRect.size.height/sourceRect.size.height);

    return transform;
}
于 2015-01-29T12:03:20.010 回答
8

我还没有找到任何一种方便的方法来解决这个问题，所以我求助于尝试过的真正的矩阵计算来实现这一点。

给定一个 CGRect A 和 CGRect B，要计算从 A 到 B 所需的转换，请执行以下操作：

CGAffineTransform transform = CGAffineTransformTranslate(CGAffineTransformIdentity, -A.origin.x, -A.origin.y);
transform = CGAffineTransformScale(transform, 1/A.size.width, 1/A.size.height);
transform = CGAffineTransformScale(transform, B.size.width, B.size.height);
transform = CGAffineTransformTranslate(transform, B.origin.x, B.origin.y);
于 2012-05-29T15:49:49.683 回答
3

这是josema.vitaminew 答案的一个变体，它也考虑了纵横比（如果您正在处理视频或图像，这很有用）：

+ (CGAffineTransform)transformFromRect:(CGRect)sourceRect toRect:(CGRect)finalRect keepingAspectRatio:(BOOL)keepingAspectRatio {
    CGAffineTransform transform = CGAffineTransformIdentity;

    transform = CGAffineTransformTranslate(transform, -(CGRectGetMidX(sourceRect)-CGRectGetMidX(finalRect)), -(CGRectGetMidY(sourceRect)-CGRectGetMidY(finalRect)));

    if (keepingAspectRatio) {
        CGFloat sourceAspectRatio = sourceRect.size.width/sourceRect.size.height;
        CGFloat finalAspectRatio = finalRect.size.width/finalRect.size.height;

        if (sourceAspectRatio > finalAspectRatio) {
            transform = CGAffineTransformScale(transform, finalRect.size.height/sourceRect.size.height, finalRect.size.height/sourceRect.size.height);
        } else {
            transform = CGAffineTransformScale(transform, finalRect.size.width/sourceRect.size.width, finalRect.size.width/sourceRect.size.width);
        }
    } else {
        transform = CGAffineTransformScale(transform, finalRect.size.width/sourceRect.size.width, finalRect.size.height/sourceRect.size.height);
    }

    return transform;
}
于 2016-04-11T01:51:45.400 回答
3

一个不错的 Swift 3 解决方案：

extension CGAffineTransform {
    init(from: CGRect, toRect to: CGRect) {
        self.init(translationX: to.midX-from.midX, y: to.midY-from.midY)
        self = self.scaledBy(x: to.width/from.width, y: to.height/from.height)
    }
}
于 2017-05-13T20:41:23.307 回答
1

上面代码片段的最后一行需要修改如下：

transform = CGAffineTransformTranslate (transform, B.origin.x*A.size.width/B.size.width, B.origin.y*A.size.height/B.size.height);

于 2014-10-11T12:52:55.837 回答
0

我开始使用 Kanobius 答案，但要么我误解了他对“纵横比”一词的使用，要么他是，因为它没有按我预期的那样执行。这是我的版本，它保持原始视图的纵横比（通过将缩放应用于 H 和 W）以实现“纵横比”行为

+ (CGAffineTransform)transformFromRect:(CGRect)sourceRect toRect:(CGRect)finalRect keepingAspectRatio:(BOOL)keepingAspectRatio
{
    CGAffineTransform transform = CGAffineTransformIdentity;

    // since the scale transform works around the midpoints, align them before doing the transform.
    transform = CGAffineTransformTranslate(transform, -(CGRectGetMidX(sourceRect)-CGRectGetMidX(finalRect)), -(CGRectGetMidY(sourceRect)-CGRectGetMidY(finalRect)));

    CGFloat originalHeight = sourceRect.size.height;
    CGFloat scaledHeight = finalRect.size.height;
    CGFloat hScalePercentage = scaledHeight / originalHeight;

    CGFloat originalWidth = sourceRect.size.width;
    CGFloat scaledWidth = finalRect.size.width;
    CGFloat wScalePercentage = scaledWidth / originalWidth;

    if (keepingAspectRatio)  
    {
        CGFloat scalePercentage = MIN(hScalePercentage, wScalePercentage);   // the most amount of scaling == smallest float number
        transform =  CGAffineTransformScale(transform, scalePercentage, scalePercentage);
    }
    else
    {
        transform = CGAffineTransformScale(transform, wScalePercentage, hScalePercentage);
    }

    return transform;
}
于 2020-02-28T01:10:34.623 回答