如何获得UIImageView的比例因子，其模式是AspectFit？ [英] how can I get the scale factor of a UIImageView who's mode is AspectFit?

问题描述

如何获得UIImageView的比例因子，其模式是AspectFit？

how can I get the scale factor of a UIImageView who's mode is AspectFit?

也就是说，我有一个模式为AspectFit的UIImageView。图像（方形）缩放到我的UIImageView框架，这很好。

That is, I have a UIImageView with mode AspectFit. The image (square) is scaled to my UIImageView frame which is fine.

如果我想获得使用的比例量（例如0.78或其他），怎么能我直接得到这个？

If I want to get the amount of scale that was used (e.g. 0.78 or whatever) how can I get this directly?

我不想比较说父视图宽度与UIImageView宽度，因为计算必须考虑方向，注意我正在将方形图像缩放为矩形视图。因此，为什么我会直接查询UIImageView以找出答案。

I don't want to have to compare say a parent view width to the UIImageView width as the calculation would have to take into account orientation, noting I'm scaling a square image into a rectangular view. Hence why I was after a direct way to query the UIImageView to find out.

编辑：我也需要它才能用于iPhone或iPad部署。

I need it to work for iPhone or iPad deployment as well.

推荐答案

我为此编写了一个UIImageView类别：

I've written a UIImageView category for that:

UIImageView + ContentScale.h

#import <Foundation/Foundation.h>

@interface UIImageView (UIImageView_ContentScale)

-(CGFloat)contentScaleFactor;

@end

UIImageView + ContentScale.m

#import "UIImageView+ContentScale.h"

@implementation UIImageView (UIImageView_ContentScale)

-(CGFloat)contentScaleFactor
{
    CGFloat widthScale = self.bounds.size.width / self.image.size.width;
    CGFloat heightScale = self.bounds.size.height / self.image.size.height;

    if (self.contentMode == UIViewContentModeScaleToFill) {
        return (widthScale==heightScale) ? widthScale : NAN;
    }
    if (self.contentMode == UIViewContentModeScaleAspectFit) {
        return MIN(widthScale, heightScale);
    }
    if (self.contentMode == UIViewContentModeScaleAspectFill) {
        return MAX(widthScale, heightScale);
    }
    return 1.0;

}

@end

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