resizing UIImage the fastest and efficient way

Question

I wanted to resize a UIImage to a certain width and height keeping the proportion in place. The simplest way to do this is:

 CGSize newSize = CGSizeMake(726,         


        

Answer 1

Here is a simple way:

    UIImage * image = [UIImage imageNamed:@"image"];
    CGSize sacleSize = CGSizeMake(10, 10); // scale image to 10 x 10
    UIGraphicsBeginImageContextWithOptions(sacleSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, sacleSize.width, sacleSize.height)];
    UIImage * resizedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

resizedImage is a new image.

Answer 2

In a performance sample of Image Resizing Techniques the score was

• 0.1420 UIKit
• 0.1722 Core Graphics
• 0.1616 Image I/O
• 2.4983 Core Image
• 2.3126 vImage

so the fastest and simplest way is:

let renderer = UIGraphicsImageRenderer(size: size)
let resized = renderer.image { (context) in
    image.draw(in: CGRect(origin: .zero, size: size))
}

Resize a UIImage the right way is from 2009 but contains useful talk about interpolation quality and preserving the aspect ratio.