Decode base64 to uiimage iOS Swift

Question

decodedData is nil but My base64String contains an extremely long string

Encode

var imgProfile:NSData = UIImagePNGRepresentation(imgUI)
let base64String = imgProfile.base64EncodedStringWithOptions(.allZeros)

Decode

let base64String = prefs.valueForKey("imgDefault") as? String         
let decodedData = NSData(base64EncodedString: base64String!, options: NSDataBase64DecodingOptions(rawValue: 0) )
var decodedimage = UIImage(data: decodedData!)

enter image description here

I"m having trouble outputting my image from base64

base64 string ENCODE before inserting into db:

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

base64 string DECODE when pulling down from db:

Optional("iVBORw0KGgoAAAANSUhEUgAAAgAAAAIACAMAAADDpiTIAAAADFBMVEXFxcX////p6enW1tbAmiBwAAAAHGlET1QAAAACAAAAAAAAAQAAAAAoAAABAAAAAQAAAAYAppse6QAABcxJREFUeAHs3et22jAQReEQ3v di8sikDaxZeGLdPTxpzS202jP9pwRkNWPDw8EEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQQAABBBBAAAEEEEAAAQQQiCVwvV4/p8fl9fH3K7cjsau2sBuBqfKvVf/x ecnDQJtKSn9qw83DQIpDLqktcV/iECCAGFuXf9Rz6o/5UHPEtTe t9V0Qj6dGCb6t9d4EBvDrzb b/3gOlvsqAjB97M/f rf/ KjUEfDuxU/nsb6APBwD/llsn/UycwDTQt1443/9MGSdCqA4eUXxK0Wv6P917xed7hJc8 m6Uw7A922O1/90MOtGXaweWXA8OXnwINKXAtSe1dzvGWcQManND9nzIZBU434MjZ/1n45zP7gVMVOPX2v1ugCZxowHnp/2wBl4tJ4CwFzm7/DwvEwCkGNND vwzQBI5XoI32/1CAAUcb0Er7fxggBg41oKH2/2WAJnCcAg3Wf/rU4HEABv Xmqw/Aw6zsq3x7xEB0596wBEStFt/Boxefwbsb0Br27/XBJie2w7u60Dr9WfA6PVnwJ4GtDz/PbPAXmAvB/qov0lw9PozYB8Dern/pyyQAts70Ojrv8/of33mfYHNB

By the way, you question suggests that you're posting data, and given the stripping of the `+` characters, it must be in a `application/x-www-form-urlencoded` request. If you change this to a [`multipart/form-data` request](http://stackoverflow.com/a/26163136/1271826), it's (a) more efficient; and (b) bypasses this base64 conversion altogether. You just need to change your server code to save it in the database as a blob instead. — Rob, Jul 11 '15 at 06:43

score 2 · Accepted Answer · edited May 23 '17 at 10:32

There are two different problems:

It would appear that the + characters have been replaced with spaces. That will happen if you submit an application/x-www-form-urlencoded request without percent escaping the + characters. This probably happened when you first sent the base64 string to be stored in the database.

See https://stackoverflow.com/a/24888789/1271826 for a discussion of some percent encoding patterns. The key point here is to not rely upon stringByAddingPercentEscapesUsingEncoding, because that will allow + characters to go unescaped.
The string is also missing the trailing = characters. (The string's length should be a multiple of four, and in this case, it's two characters short, so there should be == at the end of the rendition with the + characters in it (the "before" string). While that is sometimes a mistake made by poorly designed base64-encoders, this is not a problem that base64EncodedStringWithOptions suffers from.

In this case, it looks like a much longer base64 string must have been truncated somehow. (Your strings are suspiciously close to 1024 characters. lol.) This truncation could happen if you put the parameters in the URL rather than the body of the request. But nothing in this code sample would account for this behavior, so the problem rests elsewhere.

But look at the length of the original NSData. The base64 string should be 1/3 larger than that (plus rounded up to the nearest four characters, once you include the trailing = characters).

And, once you decode the string that you've provided and look at the actual contents, you can also see that the base64 string was truncated. (According to the portion provided, there should be 1484 bytes of IDAT data, and there's not, plus there's no IEND chunk ... don't worry about those details, but rest assured that it's basically saying that the PNG data stream is incomplete.)

I used POST when sending it to my php url. The base64 strings in my question is the full string when i encoded the image — SlopTonio, Jul 10 '15 at 20:33
@SlopTonio I've looked at the binary representation that your strings demonstrate, and it confirms the hypothesis that the base64 string was cut short somehow. In terms of how it was truncated, there's not enough in the original question to diagnose this. But it's a place for you to start your research. Regardless, see my expanded answer. — Rob, Jul 11 '15 at 06:37
Thanks Rob, your answer makes logical sense. I will try to debug this on Monday — SlopTonio, Jul 11 '15 at 15:15
I used func stringByAddingPercentEncodingForURLQueryValue() from your http://stackoverflow.com/a/24888789/1271826 answer and it worked like charm! thanks again — SlopTonio, Jul 13 '15 at 16:05
@Rob Can you please have a look on this question of mine - http://stackoverflow.com/q/36256326/5395919 — G.Abhisek, Mar 28 '16 at 06:42

score 0 · Answer 2 · edited May 23 '17 at 10:27

0

If you're getting nil returned, then your base64 string is not valid. NSData(base64EncodedString:options:) requires a base64 string that is padded with = to a multiple of 4.

Here's a similar issue (except in Obj-C). NSData won't accept valid base64 encoded string

edited May 23 '17 at 10:27

Community

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answered Jul 10 '15 at 18:12

bryanm

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I'm encoding my image and then storing it into my db as a blob. Not sure how my base64 string is invalid when pulling it down from my db and attempting to decode it? – SlopTonio Jul 10 '15 at 18:13
How large is the string? Can you post the entire thing in your question? Or in a pastebin? – bryanm Jul 10 '15 at 18:15

Decode base64 to uiimage iOS Swift

2 Answers2