如何获取 UIImageView 中缩放后的 UIImage 的大小？

Question

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

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，以便我可以在新缩放的图像上准确绘制。

有没有什么方法可以做到这一点，而无需根据 UIImageView 大小和大小自己弄清楚。 UIImage 原始大小（基本上是对其缩放进行逆向工程）？

Answer 1

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);
    }
}

Swift 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)
  }
}

Answer 2

这个简单的函数将计算图像的大小： -

[imageView setFrame:AVMakeRectWithAspectRatioInsideRect(image.size, imageView.frame)];

有关更多详细信息，您可以参考 AVMakeRectWithAspectRatioInsideRect - AVFoundation< /a>.

Answer 3

这个简单的函数将计算长宽比适合后图像的大小：

-(CGSize)imageSizeAfterAspectFit:(UIImageView*)imgview{


    float newwidth;
    float newheight;

    UIImage *image=imgview.image;

    if (image.size.height>=image.size.width){
        newheight=imgview.frame.size.height;
        newwidth=(image.size.width/image.size.height)*newheight;

        if(newwidth>imgview.frame.size.width){
            float diff=imgview.frame.size.width-newwidth;
            newheight=newheight+diff/newheight*newheight;
            newwidth=imgview.frame.size.width;
        }

    }
    else{
        newwidth=imgview.frame.size.width;
        newheight=(image.size.height/image.size.width)*newwidth;

        if(newheight>imgview.frame.size.height){
            float diff=imgview.frame.size.height-newheight;
            newwidth=newwidth+diff/newwidth*newwidth;
            newheight=imgview.frame.size.height;
        }
    }

    NSLog(@"image after aspect fit: width=%f height=%f",newwidth,newheight);


    //adapt UIImageView size to image size
    //imgview.frame=CGRectMake(imgview.frame.origin.x+(imgview.frame.size.width-newwidth)/2,imgview.frame.origin.y+(imgview.frame.size.height-newheight)/2,newwidth,newheight);

    return CGSizeMake(newwidth, newheight);

}

Answer 4

改编自 cncool 答案，迅速作为 UIImageView 扩展，也许对某人有用：

extension UIImageView{
    func frameForImageInImageViewAspectFit() -> CGRect
    {
        if  let img = self.image {
            let imageRatio = img.size.width / img.size.height;

            let viewRatio = self.frame.size.width / self.frame.size.height;

            if(imageRatio < viewRatio)
            {
                let scale = self.frame.size.height / img.size.height;

                let width = scale * img.size.width;

                let topLeftX = (self.frame.size.width - width) * 0.5;

                return CGRectMake(topLeftX, 0, width, self.frame.size.height);
            }
            else
            {
                let scale = self.frame.size.width / img.size.width;

                let height = scale * img.size.height;

                let topLeftY = (self.frame.size.height - height) * 0.5;

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

        return CGRectMake(0, 0, 0, 0)
    }
}

Answer 5

由于您已将图像视图设置为“宽高比适合”，因此您可以简单地获取图像视图的高度和宽度以及原始图像的高度和宽度，并计算缩放图像的高度和宽度。

也就是说，更好的方法是使用自定义视图而不是 UIImageView。 然后，在自定义视图中自己绘制图像。 这样你就可以控制它的各个方面。

Answer 6

继@MeetDoshi之后，这里有一个可以适应这一点的扩展。

extension UIImageView {
    /// Retrieve the scaled size of the image within this ImageView.
    /// - Returns: A CGRect representing the size of the image after scaling or nil if no image is set.
    func getScaledImageSize() -> CGRect? {
        if let image = self.image {
            return AVMakeRect(aspectRatio: image.size, insideRect: self.frame);
        }

        return nil;
    }
}

Answer 7

我编写了一个有用的扩展，将其包含在它的一组附加内容中，可能值得一看。

包含的功能

func getScaledImageSize() -> CGRect?
func getScaledImageSizeWithPadding() -> CGRect?
func getPaddingTop() -> CGFloat? {
func getPaddingBottom() -> CGFloat? {
func getPaddingLeft() -> CGFloat? {
func getPaddingRight() -> CGFloat?
func getScaledCoordinate(forX x: CGFloat, andY y: CGFloat, multiplier:CGFloat = 100.0) -> CGPoint?
func getScaledCoordinateWithPadding(forX x: CGFloat, andY y: CGFloat, multiplier:CGFloat = 100.0) -> CGPoint?

https://gist.github.com/nathan-fiscaletti /e1b85f68559f305db7342bfff9574563

Answer 8

如果填充框架时保持图像长宽比，则图像视图框架将与图像尺寸不同。

Answer 9

从框架中获取 UIImageView 的大小怎么样？ 即imageView.frame？