Pass kCGImageSourceTypeIdentifierHint as a UTI

We were passing this as a MIME type, but the key actually expects a UTI.

Fixes #62.

README.md

@@ -410,9 +410,15 @@ work by you shall be dual licensed as above, without any additional terms or con
 
 ## Version History
 
+#### Development
+
+* Fix a bug when parsing images where we passed the wrong value for the type identifier hint, resulting in a warning being logged to the console ([#62][]).
+
+[#62]: https://github.com/postmates/PMHTTP/issues/62 "Unknown Hint Identifier for Image MIME Types · Issue #62 · postmates/PMHTTP"
+
 #### v4.3.3 (2019-04-07)
 
-* Updated `PMHTTPErrorIsFailedResponse` to handle `PMHTTPErrorUnexpectedNoContent` and `PMHTTPErrorUnexpectedRedirect` in addition to `PMHTTPErrorFailedResponse` and `PMHTTPErrorUnauthorized`.
+* Update `PMHTTPErrorIsFailedResponse` to handle `PMHTTPErrorUnexpectedNoContent` and `PMHTTPErrorUnexpectedRedirect` in addition to `PMHTTPErrorFailedResponse` and `PMHTTPErrorUnauthorized`.
 * Fix warnings introduced by Xcode 10.2.
 
 #### v4.3.2 (2018-11-14)

Sources/PlatformSpecific.swift

@@ -376,8 +376,10 @@ import Foundation
             // Use CGImageSource so we can provide the MIME type hint.
             // NB: CGImageSource will cache the decoded image data by default on 64-bit platforms.
             let options: NSDictionary?
-            if let mimeType = mimeType {
-                options = [kCGImageSourceTypeIdentifierHint: mimeType as CFString]
+            if let mimeType = mimeType,
+                let uti = UTTypeCreatePreferredIdentifierForTag(kUTTagClassMIMEType, mimeType as CFString, kUTTypeImage)?.takeRetainedValue()
+            {
+                options = [kCGImageSourceTypeIdentifierHint: uti]
             } else {
                 options = nil
             }