Resize Image without losing quality

Question

I\'m using the functions below to resize my images width & height but I noticed that it ruins the image quality.

class func imageWithSize(image: UIImage,         


        

Answer 1

Here is my Objective-C code. It's work for me.

+ (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize isAspectRation:(BOOL)aspect {
    if (!image) {
        return nil;
    }
    //UIGraphicsBeginImageContext(newSize);
    // In next line, pass 0.0 to use the current device's pixel scaling factor (and thus account for Retina resolution).
    // Pass 1.0 to force exact pixel size.
    CGFloat originRatio = image.size.width / image.size.height;
    CGFloat newRatio = newSize.width / newSize.height;

    CGSize sz;

    if (!aspect) {
        sz = newSize;
    }else {
        if (originRatio < newRatio) {
            sz.height = newSize.height;
            sz.width = newSize.height * originRatio;
        }else {
            sz.width = newSize.width;
            sz.height = newSize.width / originRatio;
        }
    }
    CGFloat scale = 1.0;
    //    if([[UIScreen mainScreen]respondsToSelector:@selector(scale)]) {
    //        CGFloat tmp = [[UIScreen mainScreen]scale];
    //        if (tmp > 1.5) {
    //            scale = 2.0;
    //        }
    //    }
    sz.width /= scale;
    sz.height /= scale;
    UIGraphicsBeginImageContextWithOptions(sz, NO, scale);
    [image drawInRect:CGRectMake(0, 0, sz.width, sz.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

I saw your code in Swift. I just convert my Objective-C to Swift without test. Can you try it and let's me know. Thanks!

struct CommonUtils {
    static func imageWithImage(image: UIImage, scaleToSize newSize: CGSize, isAspectRation aspect: Bool) -> UIImage{

        let originRatio = image.size.width / image.size.height;//CGFloat
        let newRatio = newSize.width / newSize.height;

        var sz: CGSize = CGSizeZero

        if (!aspect) {
            sz = newSize
        }else {
            if (originRatio < newRatio) {
                sz.height = newSize.height
                sz.width = newSize.height * originRatio
            }else {
                sz.width = newSize.width
                sz.height = newSize.width / originRatio
            }
        }
        let scale: CGFloat = 1.0

        sz.width /= scale
        sz.height /= scale
        UIGraphicsBeginImageContextWithOptions(sz, false, scale)
        image.drawInRect(CGRectMake(0, 0, sz.width, sz.height))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
}