pg_escape_bytea() escapes string for bytea datatype. It returns escaped string.
Nota: When you SELECT bytea type, PostgreSQL returns octal byte value prefixed by \ (e.g. \032). Users are supposed to convert back to binary format by yourself.
This function requires PostgreSQL 7.2 or later. With PostgreSQL 7.2.0 and 7.2.1, bytea type must be casted when you enable multi-byte support. i.e. INSERT INTO test_table (image) VALUES ('$image_escaped'::bytea); PostgreSQL 7.2.2 or later does not need cast. Exception is when client and backend character encoding does not match, there may be multi-byte stream error. User must cast to bytea to avoid this error.
Newer PostgreSQL will support unescape function. Support for built-in unescape function will be added when it's available.
See also pg_escape_string()