1 Scope Conformance

7.4.2 ASCIIHexDecodeFilter
The ASCIIHexDecode filter decodes data that has been encoded in ASCII hexadecimal form. ASCII hexadecimal encoding and ASCII base-85 encoding (7.4.3, “ASCli85Decode Filter”) convert binary data, such as image data or previously compressed data, to 7-bit ASCII characters.

NOTE ASCII base-85 encoding is preferred to ASCII hexadecimal encoding. Base-85 encoding is preferred because it is more compact: it expands the data by a factor of 4:5, compared with 1:2 for ASCII hexadecimal encoding.

The ASCIIHexDecode filter shall produce one byte of binary data for each pair of ASCII hexadecimal digits (0-9 and A-F or a-f). All while-space characters (see 7.2. "Lexical Conventions”) shall be ignored. A GREATER-THAN SIGN (3Eh) indicates EOD. Any other characters shall cause an error if the filter encounters the EOD marker after reading an odd number of hexadecimal digits it shall behave as if a 0 (zero) followed the last digit.