ios - JSON 解析エラー Microsoft Emotion API ios

Question

Microsoft Emotion API の使用に問題があります。ドキュメントを読みましたが、使用できません。以下のコードを使用するたびに、Bad body JSON parsing error が発生します。コードの問題を検出できません。

メソッドを作成しました - (IBAction)clickToGenerateEmotion:(id)sender

NSString* path = @"https://api.projectoxford.ai/emotion/v1.0/recognize";
NSArray* array = @[
                    @"entities=true",
                   ];

NSString* string = [array componentsJoinedByString:@"&"];
path = [path stringByAppendingFormat:@"?%@", string];

NSLog(@"%@", path);

UIImage *yourImage= _image;
NSData *imageData = UIImagePNGRepresentation(yourImage);

NSMutableURLRequest* _request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:path]];
[_request setHTTPMethod:@"POST"];
[_request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[_request setValue:@"9b118d1587ce40899598b48a6c29b51a" forHTTPHeaderField:@"Ocp-Apim-Subscription-Key"];

 NSDictionary *params = @{@"\"url\"" : @"\"http://engineering.unl.edu/images/staff/Kayla_Person-small.jpg\""};

  NSMutableArray *pairs = [[NSMutableArray alloc] initWithCapacity:0];
for (NSString *key in params) {
     [pairs addObject:[NSString stringWithFormat:@"%@=%@", key, params[key]]];
   }

NSString *requestParams = [pairs componentsJoinedByString:@"&"];


[_request setHTTPBody:imageData];

NSURLResponse *response = nil;
NSError *error = nil;
NSData* _connectionData = [NSURLConnection sendSynchronousRequest:_request returningResponse:&response error:&error];
NSLog(@"responseData = %@", [[NSString alloc] initWithData:_connectionData encoding:NSUTF8StringEncoding]);
if (nil != error)
{
    NSLog(@"Error: %@", error);
}
else
{
    NSError* error = nil;
    NSMutableDictionary* json = nil;
    NSString* dataString = [[NSString alloc] initWithData:_connectionData encoding:NSUTF8StringEncoding];
    NSLog(@"%@", dataString);

    if (nil != _connectionData)
    {
        json = [NSJSONSerialization JSONObjectWithData:_connectionData options:NSJSONReadingMutableContainers error:&error];
    }

    if (error || !json)
    {
        NSLog(@"Could not parse loaded json with error:%@", error);
    }

    NSLog(@"%@", json);
    _connectionData = nil;
}
`

前もって感謝します！！！