blue-with-0x00-in-a-header.asis is a copy from ../../images/blue.png with the following prepended using Control Pictures to signify actual newlines and 0x00:
blue-with-0x00-in-a-header.asis
../../images/blue.png
HTTP/1.1 200 AN IMAGE␍␊ Content-Type: image/png␍␊ Custom: ␀␍␊␍␊