Answer: Pixel Puzzle #354

The hidden picture is a robot!

The finished pixel picture: a robot.
Here’s what the colours make.

The picture as Python

Here is the same picture stored as numbers in a Python list. The program reads each number and prints a symbol for it, so you can see the picture appear in the Python shell.

picture = [
    "0000000110000000",
    "0000000220000000",
    "0111111111111100",
    "0111111111111100",
    "0131111111113100",
    "0111111111111100",
    "0111111111111100",
    "0114444444441100",
    "0111111111111100",
    "0055555555555000",
    "0055555555555000",
    "0055555555555000",
    "0055555555555000",
    "0055555555555000",
    "0055555555555000",
    "0004004004004000",
]
symbols = " #@*o+"

for row in picture:
    line = ""
    for number in row:
        line = line + symbols[int(number)]
    print(line)

When you run it, it prints:

       ##
       @@
 #############
 #############
 #*#########*#
 #############
 #############
 ##ooooooooo##
 #############
  +++++++++++
  +++++++++++
  +++++++++++
  +++++++++++
  +++++++++++
  +++++++++++
   o  o  o  o

Squashing the picture smaller

Computers often save space with a trick called run-length encoding. Instead of storing every pixel, they count how many of the same colour are in a row. Here’s this picture written that way:

Show the run-length code
  • Row 1: 7 × white, 2 × red, 7 × white
  • Row 2: 7 × white, 2 × grey, 7 × white
  • Row 3: 1 × white, 13 × red, 2 × white
  • Row 4: 1 × white, 13 × red, 2 × white
  • Row 5: 1 × white, 1 × red, 1 × yellow, 9 × red, 1 × yellow, 1 × red, 2 × white
  • Row 6: 1 × white, 13 × red, 2 × white
  • Row 7: 1 × white, 13 × red, 2 × white
  • Row 8: 1 × white, 2 × red, 9 × navy, 2 × red, 2 × white
  • Row 9: 1 × white, 13 × red, 2 × white
  • Row 10: 2 × white, 11 × purple, 3 × white
  • Row 11: 2 × white, 11 × purple, 3 × white
  • Row 12: 2 × white, 11 × purple, 3 × white
  • Row 13: 2 × white, 11 × purple, 3 × white
  • Row 14: 2 × white, 11 × purple, 3 × white
  • Row 15: 2 × white, 11 × purple, 3 × white
  • Row 16: 3 × white, 1 × navy, 2 × white, 1 × navy, 2 × white, 1 × navy, 2 × white, 1 × navy, 3 × white