Resize an image with drawInRect while maintaining the aspect ratio like Scale Aspect Fill?

Question

I would like to resize an image with drawInRect method, but I would also like to maintain the right aspect ratio, while filling completely the given frame (as .ScaleAspectFill does for UIViewContentMode). Anyone has a ready answer for this?

Here is my code (pretty straightforward...):

func scaled100Image() -> UIImage {
    let newSize = CGSize(width: 100, height: 100)
    UIGraphicsBeginImageContext(newSize)
    self.pictures[0].drawInRect(CGRect(x: 0, y: 0, width: 100, height: 100))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage
}

Answer 1

OK, so no ready-made answer... I wrote a swift extension for UIImage, feel free to use it if you need it.

Here it is:

extension UIImage {
    func drawInRectAspectFill(rect: CGRect) {
            let targetSize = rect.size
    if targetSize == .zero {
        self.draw(in: rect)
    }
    let widthRatio    = targetSize.width  / self.size.width
    let heightRatio   = targetSize.height / self.size.height
    let scalingFactor = max(widthRatio, heightRatio)
    let newSize = CGSize(width:  self.size.width  * scalingFactor,
                         height: self.size.height * scalingFactor)
    UIGraphicsBeginImageContext(targetSize)
    let origin = CGPoint(x: (targetSize.width  - newSize.width)  / 2,
                         y: (targetSize.height - newSize.height) / 2)
    self.draw(in: CGRect(origin: origin, size: newSize))
    let scaledImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    scaledImage?.draw(in: rect)
    }
}

So in the example above, you use it like that:

self.pictures[0].drawInRectAspectFill(CGRect(x: 0, y: 0, width: 100, height: 100))

Answer 2

The Objective-C version, if someone need it(Paste this code inside a UIIMage category):

- (void) drawInRectAspectFill:(CGRect) recto {

CGSize targetSize = recto.size;
if (targetSize.width <= CGSizeZero.width && targetSize.height <= CGSizeZero.height ) {
    return  [self drawInRect:recto];
}

float widthRatio = targetSize.width  / self.size.width;
float heightRatio   = targetSize.height / self.size.height;
float scalingFactor = fmax(widthRatio, heightRatio);
CGSize newSize = CGSizeMake(self.size.width  * scalingFactor, self.size.height * scalingFactor);

UIGraphicsBeginImageContext(targetSize);

CGPoint origin = CGPointMake((targetSize.width-newSize.width)/2,(targetSize.height - newSize.height) / 2);

[self drawInRect:CGRectMake(origin.x, origin.y, newSize.width, newSize.height)];
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

[scaledImage drawInRect:recto];

}