Iphone – How to know the image size after applying aspect fit for the image in an UIImageView

If I got you right, it would be something like this: get image size by:

UIImage * img = [UIImage imageNamed:@"someImage.png"];
CGSize imgSize = img.size;

calculate scale ratio on width

float ratio=yourImageView.frame.size.width/imgSize.width;

check scaled height (using same ratio to keep aspect)

float scaledHeight=imgSize.height*ratio;
if(scaledHeight < yourImageView.frame.size.height)
{
   //update height of your imageView frame with scaledHeight
}

Either use

imageView.contentMode = UIViewContentModeScaleAspectFill;

or

imageView.contentMode = UIViewContentModeScaleAspectFit;

The first one will fill the frame, possibly cutting off parts of your image. The second one will show the entire image, possibly leaving areas of the frame open.