The mime type for .JPG files exported to the Storage Access Framework via the documents provider is the fallback application/octet-stream; thus, image viewers won't open it.

Given that file extensions are usually case insensitive and the library appears to only recognize lower-case variants (tried .html, .doc and .txt), and that digital cameras often store uppercase letters, I suggest that lowercasing the extension before here as a mitigation.

(I can't tell whether there might be better ways than using webkit's mimetypemap (maybe libmagic?) -- but lowercasing would mitigate the immediate issue).

Thank you for maintaining termux and the documents provider; it makes dealing with the android file system limitations much better!