如何在 UIImageView 中获取缩放的 UIImage 的大小?

How to get the size of a scaled UIImage in UIImageView?(如何在 UIImageView 中获取缩放的 UIImage 的大小?)

问题描述

UIImageView 的image.size 属性给出了原始UIImage 的大小.我想知道将自动缩放图像放入 UIImageView 时的大小(通常小于原始图像).

The image.size attribute of UIImageView gives the size of the original UIImage. I would like to find out the size of the autoscaled image when it is put in the UIImageView (typically smaller than the original).

例如，我将图像设置为 Aspect Fit.现在我想知道它在屏幕上的新高度和宽度，以便在新缩放的图像上准确地绘制.

For example, I have the image set to Aspect Fit. Now I want to know its new height and width on the screen so I can draw accurately on the new scaled image.

有没有什么方法可以做到这一点，而无需自己根据 UIImageView 的大小来解决?UIImage 原始大小(基本上是对其缩放进行逆向工程)?

Is there any way to do this without figuring it out myself based on the UIImageView size & UIImage original size (basically reverse engineering its scaling)?

推荐答案

Objective-C:

-(CGRect)frameForImage:(UIImage*)image inImageViewAspectFit:(UIImageView*)imageView
{
    float imageRatio = image.size.width / image.size.height;
    float viewRatio = imageView.frame.size.width / imageView.frame.size.height;
    if(imageRatio < viewRatio)
    {
        float scale = imageView.frame.size.height / image.size.height;
        float width = scale * image.size.width;
        float topLeftX = (imageView.frame.size.width - width) * 0.5;
        return CGRectMake(topLeftX, 0, width, imageView.frame.size.height);
    }
    else
    {
        float scale = imageView.frame.size.width / image.size.width;
        float height = scale * image.size.height;
        float topLeftY = (imageView.frame.size.height - height) * 0.5;

        return CGRectMake(0, topLeftY, imageView.frame.size.width, height);
    }
}

斯威夫特 4:

func frame(for image: UIImage, inImageViewAspectFit imageView: UIImageView) -> CGRect {
  let imageRatio = (image.size.width / image.size.height)
  let viewRatio = imageView.frame.size.width / imageView.frame.size.height
  if imageRatio < viewRatio {
    let scale = imageView.frame.size.height / image.size.height
    let width = scale * image.size.width
    let topLeftX = (imageView.frame.size.width - width) * 0.5
    return CGRect(x: topLeftX, y: 0, width: width, height: imageView.frame.size.height)
  } else {
    let scale = imageView.frame.size.width / image.size.width
    let height = scale * image.size.height
    let topLeftY = (imageView.frame.size.height - height) * 0.5
    return CGRect(x: 0.0, y: topLeftY, width: imageView.frame.size.width, height: height)
  }
}

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