Printable characters usually refers to the 7-bit ASCII set of characters, including space (32), excluding the control chars 0 to 31 and 127.
The process of converting binary to printable is called ASCII (American Standard Code for Information Interchange) armouring, especially in the context of certificates and encryption.
Font.canDisplay is not much use. It lies and claims to be able to render a glyph when all it can do is display some generic missing character gylph.
Here is a rough way to decide if a character will likely be printable. Adjust as necessary:
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