downsize image

    NSURL *imageUrl;
    CGImageSourceRef imageScorce = CGImageSourceCreateWithURL((__bridge CFURLRef)imageUrl, nil);
    NSDictionary *options = @{(__bridge NSString *)kCGImageSourceCreateThumbnailFromImageIfAbsent:(id)kCFBooleanTrue,
                              (__bridge NSString *)kCGImageSourceCreateThumbnailWithTransform:(id)kCFBooleanTrue,
                              (__bridge NSString *)kCGImageSourceThumbnailMaxPixelSize:@128};
    CFRelease(imageScorce);
    
    CGImageRef thumbImageRef = CGImageSourceCreateThumbnailAtIndex(imageScorce, 0, (__bridge CFDictionaryRef)options);
    NSURL *targetUrl;
    CGImageDestinationRef destinationRef = CGImageDestinationCreateWithURL((__bridge CFURLRef)targetUrl, kUTTypeJPEG, 1, nil);
    if (!destinationRef) {
        return;
    }
    NSDictionary *properties = @{(__bridge NSString *)kCGImageDestinationLossyCompressionQuality:@(0.94)};
    CGImageDestinationSetProperties(destinationRef, (__bridge CFDictionaryRef)properties);
    CGImageDestinationAddImage(destinationRef, thumbImageRef, NULL);
    bool ret = CGImageDestinationFinalize(destinationRef);
    CFRelease(destinationRef);