Can you save an edited RAW .dng file on iOS?

Question

I want to build an iOS 10 app that lets you shoot a RAW (.dng) image, edit it, and then saved the edited .dng file to the camera roll. By combining

Answer 1

Unfortunately DNG isn't supported as an output format in Apple's ImageIO framework. See the output of CGImageDestinationCopyTypeIdentifiers() for a list of supported output types:

(
    "public.jpeg",
    "public.png",
    "com.compuserve.gif",
    "public.tiff",
    "public.jpeg-2000",
    "com.microsoft.ico",
    "com.microsoft.bmp",
    "com.apple.icns",
    "com.adobe.photoshop-image",
    "com.adobe.pdf",
    "com.truevision.tga-image",
    "com.sgi.sgi-image",
    "com.ilm.openexr-image",
    "public.pbm",
    "public.pvr",
    "org.khronos.astc",
    "org.khronos.ktx",
    "com.microsoft.dds",
    "com.apple.rjpeg"
)