Ensures a string is a valid Data URI for base64-encoded content. Returns as-is if already a Data URI, otherwise prepends the appropriate prefix.
Base64 string or existing Data URI
MIME type for base64 input (default: "application/octet-stream")
Proper Data URI string
Ensures a string is a valid Data URI for base64-encoded content. Returns as-is if already a Data URI, otherwise prepends the appropriate prefix.