アスペクト比を保ってUIImageをリサイズ

resizeAspectFitWithSize.m

/**
 * アスペクト比を保ってUIImageをリサイズ
 *
 */
+ (UIImage *)resizeAspectFitWithSize:(UIImage *)srcImg size:(CGSize)size
{
    CGFloat widthRatio  = size.width  / srcImg.size.width;
    CGFloat heightRatio = size.height / srcImg.size.height;
    CGFloat ratio = (widthRatio < heightRatio) ? widthRatio : heightRatio;
    
    CGSize resizedSize = CGSizeMake(srcImg.size.width*ratio, srcImg.size.height*ratio);
    
    UIGraphicsBeginImageContext(resizedSize);
    [srcImg drawInRect:CGRectMake(0, 0, resizedSize.width, resizedSize.height)];
    UIImage* resizedImage = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
    return resizedImage;
}