UIImage as Representation but no file extension

Question

I want to convert an image to either

UIImagePNGRepresentation
UIImageJPEGRepresentation

however I do not know the file type. I've just got a URL with no extension. Is there anyway to save the image from the URL to the filesystem?

// got the data from the URL

let imageData = UIImage(data: data!)

// now I want to write to the filesystem but only way was with a representation as UIImage has no write

if let saveImageData = UIImageXXXXXXRepresentation(imageData!) {
try saveImageData.write(to: URL(fileURLWithPath: localFilename), options: [.atomic])
}

You already have the image data in `data`. Why convert to an UIImage and back? — Martin R, Mar 29 '17 at 09:58

score 4 · Accepted Answer · edited May 23 '17 at 12:34

Get the imageData from URL and then check the image type as below from that data object

Swift 3

let data: Data = UIImagePNGRepresentation(yourImage)!

extension Data {
    var format: String {
        let array = [UInt8](self)
        let ext: String
        switch (array[0]) {
        case 0xFF:
            ext = "jpg"
        case 0x89:
            ext = "png"
        case 0x47:
            ext = "gif"
        case 0x49, 0x4D :
            ext = "tiff"
        default:
            ext = "unknown"
        }
        return ext
    }
}

Objective C

+ (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;
}

After checking above you can store the image with selected extension

For getting extension from data you can check from here also

Please add proper attribution if code from other answers: http://stackoverflow.com/a/5042365/1187415, http://stackoverflow.com/a/40317201/1187415. — Martin R, Mar 29 '17 at 10:05
if you taken the code from another place please mention in your answer, — Anbu.Karthik, Mar 29 '17 at 10:12

handiansom · Answer 2 · 2017-03-29T10:13:29.540

0

Use that method to check the extension of your image by using the NSData of your image.

func contentTypeForImageData(data: NSData) -> String {
    var c: UInt8
    data.getBytes(c, length: 1)
    switch c {
        case 0xFF:
            return "image/jpeg"
        case 0x89:
            return "image/png"
        case 0x47:
            return "image/gif"
        case 0x49, 0x4D:
            return "image/tiff"
    }

    return nil
}

edited Mar 29 '17 at 10:13

answered Mar 29 '17 at 09:58

handiansom

783
11
27

That is Objective-C, not Swift. And it looks like a verbatim copy of http://stackoverflow.com/a/5042365/1187415, without attribution. – Martin R Mar 29 '17 at 10:00

UIImage as Representation but no file extension

2 Answers2