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

Question

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

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

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

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.

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

Answer 1

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