Resizing a UIImage, leveraging UIViewContentMode

UIImage+Resizing.m

- (UIImage *)resizedWithNewSize:(CGSize)size contentMode:(UIViewContentMode)contentMode {
    CGFloat x = 0.0f;
    CGFloat y = 0.0f;
    CGFloat w = size.width;
    CGFloat h = size.height;
    BOOL scale = YES;
    switch (contentMode) {
        case UIViewContentModeScaleToFill: {
            break;
        }
        case UIViewContentModeScaleAspectFit: {
            CGFloat ratio = w / self.size.width;
            if(self.size.height * ratio > h) {
                ratio = h / self.size.height;
            }
            w = self.size.width * ratio;
            h = self.size.height * ratio;
            break;
        }
        case UIViewContentModeScaleAspectFill: {
            CGFloat ratio = w / self.size.width;
            if(self.size.height * ratio < h) {
                ratio = h / self.size.height;
            }
            w = self.size.width * ratio;
            h = self.size.height * ratio;
            break;
        }
        case UIViewContentModeRedraw: {
            scale = NO;
            break;
        }
        case UIViewContentModeCenter: {
            CGFloat xInset = (self.size.width - w) / 2.0f;
            CGFloat yInset = (self.size.height - h) / 2.0f;
            x = -xInset;
            y = -yInset;
            scale = NO;
            break;
        }
        case UIViewContentModeTop: {
            CGFloat xInset = (self.size.width - w) / 2.0f;
            x = -xInset;
            scale = NO;
            break;
        }
        case UIViewContentModeBottom: {
            CGFloat xInset = (self.size.width - w) / 2.0f;
            CGFloat yOffset = (self.size.height - h);
            x = -xInset;
            y= yOffset;
            scale = NO;
            break;
        }
        case UIViewContentModeLeft: {
            CGFloat yInset = (self.size.height - h) / 2.0f;
            y = -yInset;
            scale = NO;
            break;
        }
        case UIViewContentModeRight: {
            CGFloat yInset = (self.size.height - h) / 2.0f;
            CGFloat xOffset = (self.size.width - w);
            y = -yInset;
            x = xOffset;
            scale = NO;
            break;
        }
        case UIViewContentModeTopLeft: {
            scale = NO;
            break;
        }
        case UIViewContentModeTopRight: {
            CGFloat xOffset = (self.size.width - w);
            x = xOffset;
            scale = NO;
            break;
        }
        case UIViewContentModeBottomLeft: {
            CGFloat yOffset = (self.size.height - h);
            y = yOffset;
            scale = NO;
            break;
        }
        case UIViewContentModeBottomRight: {
            CGFloat xOffset = (self.size.width - w);
            CGFloat yOffset = (self.size.height - h);
            x = xOffset;
            y = yOffset;
            scale = NO;
            break;
        }
        default: {
            break;
        }
    }
    
    UIGraphicsBeginImageContext(CGSizeMake(w, h));
    CGRect drawingRect = scale ? CGRectMake(x, y, w, h) : CGRectMake(x, y, self.size.width, self.size.height);
    [self drawInRect:drawingRect];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}