Determine Mime Type from Nsdata

Finding image type from NSData or UIImage

If you have NSData for the image file, then you can guess at the content type by looking at the first byte:

+ (NSString *)contentTypeForImageData:(NSData *)data {
    uint8_t c;
    [data getBytes:&c length:1];

    switch (c) {
    case 0xFF:
        return @"image/jpeg";
    case 0x89:
        return @"image/png";
    case 0x47:
        return @"image/gif";
    case 0x49:
    case 0x4D:
        return @"image/tiff";
    }
    return nil;
}

How can you read a files MIME-type in objective-c

It's a bit hacky, but it should work, don't know for sure because I'm just guessing at it

There are two options:

1. If you just need the MIME type, use the timeoutInterval: NSURLRequest.
2. If you want the data as well, you should use the commented out NSURLRequest.

Make sure to perform the request in a thread though, since it's synchronous.

NSString* filePath = [[NSBundle mainBundle] pathForResource:@"imagename" ofType:@"jpg"];
NSString* fullPath = [filePath stringByExpandingTildeInPath];
NSURL* fileUrl = [NSURL fileURLWithPath:fullPath];
//NSURLRequest* fileUrlRequest = [[NSURLRequest alloc] initWithURL:fileUrl];
NSURLRequest* fileUrlRequest = [[NSURLRequest alloc] initWithURL:fileUrl cachePolicy:NSURLCacheStorageNotAllowed timeoutInterval:.1];

NSError* error = nil;
NSURLResponse* response = nil;
NSData* fileData = [NSURLConnection sendSynchronousRequest:fileUrlRequest returningResponse:&response error:&error];

fileData; // Ignore this if you're using the timeoutInterval
          // request, since the data will be truncated.

NSString* mimeType = [response MIMEType];

[fileUrlRequest release];

How to determine appropriate file extension from MIME Type in Objective-C

Credit goes to @makadev for this link which he posted as a comment, but I thought I would add it as an actual answer. Here's some code derived from that article, which worked on iOS 11. Note that you'll need to link with / import the MobileCoreServices framework. The value you fill in for the mimetype token below should be an NSString*.

NSString* uti = (__bridge_transfer NSString*)UTTypeCreatePreferredIdentifierForTag(kUTTagClassMIMEType, (__bridge CFStringRef)<#mimetype#>, NULL);
NSString* extension = (__bridge_transfer NSString*)UTTypeCopyPreferredTagWithClass((__bridge CFStringRef)uti, kUTTagClassFilenameExtension);

Path extension and MIME type of file in swift

Assuming you are receiving your data as NSData, follow this Post: https://stackoverflow.com/a/5042365/2798777

In Swift for example:

var c = [UInt32](count: 1, repeatedValue: 0)
(data as! NSData).getBytes(&c, length: 1)
switch (c[0]) {
case 0xFF, 0x89, 0x00:
    println("image")
case 0x47:
    println("gif")
default: 
    println("unknown: \(c[0])")
}

Finding video type from NSData

You should check the content type returned by the server:

- (void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)theResponse
  {
    NSString* content_type = [[(NSHTTPURLResponse*)theResponse allHeaderFields] valueForKey:@"Content-Type"];

    //content_type might be image/jpeg, video/mp4 etc.
  }

Convert NSData into Default MIME type

NSData is just raw data.

So you have two primary options:

• 1) transfer the type
• or 2) work with a small set of types you recognize, and programmatically determine the type based on the file formats you receive as input. For example, a pdf's first 4 bytes may be %PDF.

If you are working with a small set of formats, you could likely determine the type of data based on the contents of the data. So you might see some APIs which are able to figure out the type the data represents when it has a handful of supported formats which it can identify… but to determine any data would take a long time to process, and to implement. It would also have a fairly high failure rate, due to all the data types/formats available -- published and unpublished, and data formats which don't necessarily have data sequences which identify them uniquely.

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