Adobe version

Adobe adopted the basic btoa encoding, but with slight changes, and gave it the name Ascii85. In particular, Adobe use the delimiters "<~" and "~>" to mark the beginning and end of an Ascii85-encoded string, and represent the length by truncating the final group.

While it is simple to pad the final 1–3 bytes with zero bytes, and then output only the first 2–4 characters of the encoded output, decoding this requires some care. Truncating the encoded characters has a rounding-down effect. To decode the final block it is necessary to round up by padding it with "u" characters, then you can decode the block and truncate the unused trailing bytes.