ios - UIImage Aspect Fit when using drawInRect?

Question

UIView provides for the "aspect fit" content mode. However, I've subclasses UIView and would like to draw a UIImage using drawInRect with an aspect fit. Is there any way for me to access that functionality without using a UIImageView?

Answer 1

The math for that is a little bit hairy, but fortunately, here's a solution I prepared earlier:

- (UIImage *)imageScaledToSize:(CGSize)size
{
    //create drawing context
    UIGraphicsBeginImageContextWithOptions(size, NO, 0.0f);

    //draw
    [self drawInRect:CGRectMake(0.0f, 0.0f, size.width, size.height)];

    //capture resultant image
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

- (UIImage *)imageScaledToFitSize:(CGSize)size
{
    //calculate rect
    CGFloat aspect = self.size.width / self.size.height;
    if (size.width / aspect <= size.height)
    {
        return [self imageScaledToSize:CGSizeMake(size.width, size.width / aspect)];
    }
    else
    {
        return [self imageScaledToSize:CGSizeMake(size.height * aspect, size.height)];
    }
}

The first function is equivalent to "scale to fill", the second (which calls the first) is equivalent to "aspect fit". These methods were written as a category on UIImage so to use them from within another class you'll need to tweak them by passing the image in as a second parameter (or just make a category on UIImage like I did).