在UIImageView中应用适合图像的宽高比后，如何知道图像大小

时间：2011-06-08 12:45:19

标签： iphone ipad uiimageview uiimage aspect-ratio

我正在将图像加载到图像视图，模式为“Aspect Fit”。我需要知道我的图像缩放到的大小。请帮忙。

20 个答案:

答案 0 :(得分：131)

为什么不使用操作系统功能AVMakeRectWithAspectRatioInsideRect？

答案 1 :(得分：51)

我想在不包含AVFoundation框架的情况下使用AVMakeRectWithAspectRatioInsideRect() 。

所以我实现了以下两个实用程序函数：

CGSize CGSizeAspectFit(CGSize aspectRatio, CGSize boundingSize)
{
    float mW = boundingSize.width / aspectRatio.width;
    float mH = boundingSize.height / aspectRatio.height;
    if( mH < mW )
        boundingSize.width = boundingSize.height / aspectRatio.height * aspectRatio.width;
    else if( mW < mH )
        boundingSize.height = boundingSize.width / aspectRatio.width * aspectRatio.height;
    return boundingSize;
}

CGSize CGSizeAspectFill(CGSize aspectRatio, CGSize minimumSize)
{
    float mW = minimumSize.width / aspectRatio.width;
    float mH = minimumSize.height / aspectRatio.height;
    if( mH > mW )
        minimumSize.width = minimumSize.height / aspectRatio.height * aspectRatio.width;
    else if( mW > mH )
        minimumSize.height = minimumSize.width / aspectRatio.width * aspectRatio.height;
    return minimumSize;
}

编辑：通过删除重复的部分进行优化。 

CGSize CGSizeAspectFit(const CGSize aspectRatio, const CGSize boundingSize)
{
    CGSize aspectFitSize = CGSizeMake(boundingSize.width, boundingSize.height);
    float mW = boundingSize.width / aspectRatio.width;
    float mH = boundingSize.height / aspectRatio.height;
    if( mH < mW )
        aspectFitSize.width = mH * aspectRatio.width;
    else if( mW < mH )
        aspectFitSize.height = mW * aspectRatio.height;
    return aspectFitSize;
}

CGSize CGSizeAspectFill(const CGSize aspectRatio, const CGSize minimumSize)
{
    CGSize aspectFillSize = CGSizeMake(minimumSize.width, minimumSize.height);
    float mW = minimumSize.width / aspectRatio.width;
    float mH = minimumSize.height / aspectRatio.height;
    if( mH > mW )
        aspectFillSize.width = mH * aspectRatio.width;
    else if( mW > mH )
        aspectFillSize.height = mW * aspectRatio.height;
    return aspectFillSize;
}

编辑结束

这需要给定大小（第一个参数）并保持其宽高比。然后在不违反宽高比的情况下尽可能多地填充给定边界（第二个参数）。

用这个回答原来的问题：

// Using aspect fit, scale the image (size) to the image view's size.
CGSize sizeBeingScaledTo = CGSizeAspectFit(theImage.size, theImageView.frame.size);

注意图像如何确定纵横比，而图像视图决定要填充的尺寸。

非常欢迎反馈。

答案 2 :(得分：30)

请参阅@ Paul-de-Lange的回答，而不是

我在一个易于访问的变量中找不到任何东西，所以这是蛮力的方式：

- (CGSize) aspectScaledImageSizeForImageView:(UIImageView *)iv image:(UIImage *)im {

float x,y;
float a,b;
x = iv.frame.size.width;
y = iv.frame.size.height;
a = im.size.width;
b = im.size.height;

if ( x == a && y == b ) {           // image fits exactly, no scaling required
    // return iv.frame.size;
}
else if ( x > a && y > b ) {         // image fits completely within the imageview frame
    if ( x-a > y-b ) {              // image height is limiting factor, scale by height
        a = y/b * a;
        b = y;
    } else {
        b = x/a * b;                // image width is limiting factor, scale by width
        a = x;
    }
} 
else if ( x < a && y < b ) {        // image is wider and taller than image view
    if ( a - x > b - y ) {          // height is limiting factor, scale by height
        a = y/b * a;
        b = y;
    } else {                        // width is limiting factor, scale by width
        b = x/a * b;
        a = x;
    }
}
else if ( x < a && y > b ) {        // image is wider than view, scale by width
    b = x/a * b;
    a = x;
}
else if ( x > a && y < b ) {        // image is taller than view, scale by height
    a = y/b * a;
    b = y;
}
else if ( x == a ) {
    a = y/b * a;
    b = y;
} else if ( y == b ) {
    b = x/a * b;
    a = x;
}
return CGSizeMake(a,b);

}

答案 3 :(得分：14)

这个简单的函数将在宽高比拟合后计算图像的大小：

    -(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);

}

答案 4 :(得分：9)

我还想在应用宽高比后计算高度，以便能够计算表视图单元格的高度。所以，我通过很少的数学实现了

ratio = width / height

并且高度将变为

height = width / ratio

因此代码段将是

UIImage *img = [UIImage imageNamed:@"anImage"];
float aspectRatio = img.size.width/img.size.height;
float requiredHeight = self.view.bounds.size.width / aspectRatio;

答案 5 :(得分：8)

对于Swift，请使用以下代码 

func imageSizeAspectFit(imgview: UIImageView) -> CGSize {
        var newwidth: CGFloat
        var newheight: CGFloat
        let image: UIImage = imgFeed.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 {
                let diff: CGFloat = 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 {
                let diff: CGFloat = imgview.frame.size.height - newheight
                newwidth = newwidth + diff / newwidth * newwidth
                newheight = imgview.frame.size.height
            }
        }

       print(newwidth, newheight)
        //adapt UIImageView size to image size
        return CGSizeMake(newwidth, newheight)
    }

和通话功能 

imgFeed.sd_setImageWithURL(NSURL(string:"Your image URL")))
self.imageSizeAfterAspectFit(imgFeed)

答案 6 :(得分：7)

也许不适合你的情况，但这个简单的方法在类似的情况下解决了我的问题：

    UIImageView *imageView = [[UIImageView alloc] initWithImage:bigSizeImage];
    [imageView sizeToFit];

如果查询 imageView.frame.size ，图像视图执行sizeToFit后，您将获得适合新图像大小的新图像视图大小。

答案 7 :(得分：7)

Swift 3 人类可读版本

extension UIImageView {

    /// Find the size of the image, once the parent imageView has been given a contentMode of .scaleAspectFit
    /// Querying the image.size returns the non-scaled size. This helper property is needed for accurate results.
    var aspectFitSize: CGSize {
        guard let image = image else { return CGSize.zero }

        var aspectFitSize = CGSize(width: frame.size.width, height: frame.size.height)
        let newWidth: CGFloat = frame.size.width / image.size.width
        let newHeight: CGFloat = frame.size.height / image.size.height

        if newHeight < newWidth {
            aspectFitSize.width = newHeight * image.size.width
        } else if newWidth < newHeight {
            aspectFitSize.height = newWidth * image.size.height
        }

        return aspectFitSize
    }

    /// Find the size of the image, once the parent imageView has been given a contentMode of .scaleAspectFill
    /// Querying the image.size returns the non-scaled, vastly too large size. This helper property is needed for accurate results.
    var aspectFillSize: CGSize {
        guard let image = image else { return CGSize.zero }

        var aspectFillSize = CGSize(width: frame.size.width, height: frame.size.height)
        let newWidth: CGFloat = frame.size.width / image.size.width
        let newHeight: CGFloat = frame.size.height / image.size.height

        if newHeight > newWidth {
            aspectFillSize.width = newHeight * image.size.width
        } else if newWidth > newHeight {
            aspectFillSize.height = newWidth * image.size.height
        }

        return aspectFillSize
    }

}

答案 8 :(得分：5)

+(UIImage *)CreateAResizeImage:(UIImage *)Img ThumbSize:(CGSize)ThumbSize 
{
    float actualHeight = Img.size.height;
    float actualWidth = Img.size.width;

    if(actualWidth==actualHeight) 
    {
        actualWidth = ThumbSize.width; 
        actualHeight = ThumbSize.height;
    }

    float imgRatio = actualWidth/actualHeight;
    float maxRatio = ThumbSize.width/ThumbSize.height; //320.0/480.0;


    if(imgRatio!=maxRatio)
    {
        if(imgRatio < maxRatio)
        {
            imgRatio = ThumbSize.height / actualHeight; //480.0 / actualHeight;
            actualWidth = imgRatio * actualWidth;
            actualHeight = ThumbSize.height; //480.0;
        }
        else
        {
            imgRatio = ThumbSize.width / actualWidth; //320.0 / actualWidth;
            actualHeight = imgRatio * actualHeight;
            actualWidth = ThumbSize.width; //320.0;
        }
    } 
    else 
    {
        actualWidth = ThumbSize.width;
        actualHeight = ThumbSize.height; 
    }


    CGRect rect = CGRectMake(0, 0, (int)actualWidth, (int)actualHeight);
    UIGraphicsBeginImageContext(rect.size);
    [Img drawInRect:rect];
    UIImage *NewImg = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return NewImg;
}

答案 9 :(得分：3)

Swift 4： .aspectFit图片的框架为 - 

import AVFoundation

let x: CGRect = AVMakeRect(aspectRatio: myImage.size, insideRect: sampleImageView.frame)

答案 10 :(得分：2)

接受的答案非常复杂，并且在某些边缘案例中失败了。我认为这个解决方案更加优雅：

- (CGSize) sizeOfImage:(UIImage*)image inAspectFitImageView:(UIImageView*)imageView
{
    UKAssert(imageView.contentMode == UIViewContentModeScaleAspectFit, @"Image View must use contentMode = UIViewContentModeScaleAspectFit");

    CGFloat imageViewWidth = imageView.bounds.size.width;
    CGFloat imageViewHeight = imageView.bounds.size.height;

    CGFloat imageWidth = image.size.width;
    CGFloat imageHeight = image.size.height;

    CGFloat scaleFactor = MIN(imageViewWidth / imageWidth, imageViewHeight / imageHeight);

    return CGSizeMake(image.size.width*scaleFactor, image.size.height*scaleFactor);
}

答案 11 :(得分：2)

以下是我解决同样问题的方法： https://github.com/alexgarbarev/UIImageView-ImageFrame

优点：

  • 支持UIViewContentMode模式
  • 可以分别查询比例和矩形
  • 可以直接从UIImageView
    • 询问图像框架

答案 12 :(得分：2)

这一行可以完成这项工作

CGSize sizeInView = AVMakeRectWithAspectRatioInsideRect（imgViewFake.image.size，imgViewFake.bounds）.size;

答案 13 :(得分：2)

Swift 3 UIImageView扩展程序：

import AVFoundation

extension UIImageView {
  var imageSize: CGSize {
    if let image = image {
      return AVMakeRect(aspectRatio: image.size, insideRect: bounds).size
    }
    return CGSize.zero
  }  
}

答案 14 :(得分：2)

这是我的AVFoundation-less解决方案。

首先，这是一个CGSize扩展，用于计算适合其他大小的大小：

extension CGSize
{
    func sizeThatFitsSize(_ aSize: CGSize) -> CGSize
    {
        let width = min(self.width * aSize.height / self.height, aSize.width)
        return CGSize(width: width, height: self.height * width / self.width)
    }
}

因此OP问题的解决方案可以归结为：

let resultSize = image.size.sizeThatFitsSize(imageView.bounds.size)

此处还有另一个扩展，用于在另一个rect中安装rect（它使用上面的CGSize扩展）：

extension CGRect
{
    func rectThatFitsRect(_ aRect:CGRect) -> CGRect
    {
        let sizeThatFits = self.size.sizeThatFitsSize(aRect.size)

        let xPos = (aRect.size.width - sizeThatFits.width) / 2
        let yPos = (aRect.size.height - sizeThatFits.height) / 2

        let ret = CGRect(x: xPos, y: yPos, width: sizeThatFits.width, height: sizeThatFits.height)
        return ret
    }
}

答案 15 :(得分：1)

Swift 4版本 

extension CGSize {
   enum AspectMode {
       case fit
       case fill
   }

   enum Orientation {
       case portrait
       case landscape
   }

   func aspectCorrectSizeToFit(targetSize: CGSize, aspectMode: AspectMode = .fill) -> CGSize {
        switch aspectMode {
        case .fill: return aspectFill(targetSize: targetSize)
        case .fit: return aspectFit(targetSize: targetSize)
        }
    }

    var orientation: Orientation {
        if height >= width { return .portrait }
        else { return .landscape }
    }

    func aspectFit(targetSize: CGSize) -> CGSize {
        let wRatio = targetSize.width / width
        let hRatio = targetSize.height / height
        let scale = min(wRatio, hRatio)
        return applying(CGAffineTransform(scaleX: scale, y: scale))
    }

    func aspectFill(targetSize: CGSize) -> CGSize {
        let wRatio = targetSize.width / width
        let hRatio = targetSize.height / height
        let scale = max(wRatio, hRatio)
        return applying(CGAffineTransform(scaleX: scale, y: scale))
    }
}

答案 16 :(得分：1)

如果您只知道图像视图的宽度，并且图像的高度是动态的，那么您需要根据给定的宽度缩放图像的高度，以移除图像上方和下方的空白区域。使用here中的以下方法根据屏幕的标准宽度缩放图像的高度。

-(UIImage*)imageWithImage: (UIImage*) sourceImage scaledToWidth: (float) i_width
{
    float oldWidth = sourceImage.size.width;
    float scaleFactor = i_width / oldWidth;

    float newHeight = sourceImage.size.height * scaleFactor;
    float newWidth = oldWidth * scaleFactor;

    UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight));
    [sourceImage drawInRect:CGRectMake(0, 0, newWidth, newHeight)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newImage;
}

从你的cellForRowAtIndexPath：方法中调用它：

UIImage *img = [dictImages objectForKey:yourImageKey]; // loaded the image
cell.imgView.image = [self imageWithImage:img scaledToWidth:self.view.frame.size.width];

答案 17 :(得分：1)

我在Swift中使用以下内容：

private func CGSizeAspectFit(aspectRatio:CGSize,boundingSize:CGSize) -> CGSize
{
    var aspectFitSize = boundingSize
    let mW = boundingSize.width / aspectRatio.width
    let mH = boundingSize.height / aspectRatio.height
    if( mH < mW )
    {
        aspectFitSize.width = mH * aspectRatio.width
    }
    else if( mW < mH )
    {
        aspectFitSize.height = mW * aspectRatio.height
    }
    return aspectFitSize
}

private func CGSizeAspectFill(aspectRatio:CGSize,minimumSize:CGSize) -> CGSize
{
    var aspectFillSize = minimumSize
    let mW = minimumSize.width / aspectRatio.width
    let mH = minimumSize.height / aspectRatio.height
    if( mH > mW )
    {
        aspectFillSize.width = mH * aspectRatio.width
    }
    else if( mW > mH )
    {
        aspectFillSize.height = mW * aspectRatio.height
    }
    return aspectFillSize
}

我这样使用它：

let aspectSize  = contentMode == .ScaleAspectFill ? CGSizeAspectFill(oldSize,minimumSize: newSize) : CGSizeAspectFit(oldSize, boundingSize: newSize)

let newRect = CGRect( x: (newSize.width - aspectSize.width)/2, y: (newSize.height - aspectSize.height)/2, width: aspectSize.width, height: aspectSize.height)

CGContextSetFillColorWithColor(context,IOSXColor.whiteColor().CGColor)
CGContextFillRect(context, CGRect(origin: CGPointZero,size: newSize))
CGContextDrawImage(context, newRect, cgImage)

答案 18 :(得分：0)

Swift 5 扩展

extension CGSize {
    func aspectFit(to size: CGSize) -> CGSize {
        let mW = size.width / self.width;
        let mH = size.height / self.height;
        
        var result = size
        if( mH < mW ) {
            result.width = size.height / self.height * self.width;
        }
        else if( mW < mH ) {
            result.height = size.width / self.width * self.height;
        }
        
        return result;
    }
    
    func aspectFill(to size: CGSize) -> CGSize {
        let mW = size.width / self.width;
        let mH = size.height / self.height;
        
        var result = size
        if( mH > mW ) {
            result.width = size.height / self.height * self.width;
        }
        else if( mW > mH ) {
            result.height = size.width / self.width * self.height;
        }
        return result;
    }
}

答案 19 :(得分：0)

上述方法从未给出所需的值。由于纵横比保持相同的纵横比，我们只需要简单的数学来计算值

检测宽高比

CGFloat imageViewAspectRatio = backgroundImageView.bounds.size.width / backgroundImageView.bounds.size.height;
CGFloat imageAspectRatio =  backgroundImageView.image.size.width / backgroundImageView.image.size.height;
CGFloat mulFactor = imageViewAspectRatio/imageAspectRatio;

获取新值

CGFloat newImageWidth = mulFactor * backgroundImageView.bounds.size.width;
CGFloat newImageHeight = mulFactor * backgroundImageView.bounds.size.height;
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