This image was produced from the third radio transmission using previously contributed code <radio-transmission-recording>.
This partly annotated version of the image was made using code from message #2 <message2-code>.
Contributed by Discord user @pink_snow.
Looks like the bottom left additional pixel is used to indicate negative numbers.
message3-decoded.txt
Revised version of the Python code that supports negative numbers is published on the message #2 page <message2-code>.
Contributed by Discord user @pink_snow.
Example output:
@pink_snow also provided a Haskell version of the same code.
annotate.hs