Answer: Pixel Puzzle #232

The hidden picture is Beep the robot!

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 = [
    "000011000000",
    "000022000000",
    "033333333300",
    "032222222300",
    "032422242300",
    "032222222300",
    "032244422300",
    "033333333300",
    "000555500000",
    "066666666600",
    "066671766600",
    "066666666600",
]
symbols = " #@*o+=%"

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

When you run it, it prints:

    ##
    @@
 *********
 *@@@@@@@*
 *@o@@@o@*
 *@@@@@@@*
 *@@ooo@@*
 *********
   ++++
 =========
 ===%#%===
 =========

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: 4 × white, 2 × pink, 6 × white
• Row 2: 4 × white, 2 × navy, 6 × white
• Row 3: 1 × white, 9 × teal, 2 × white
• Row 4: 1 × white, 1 × teal, 7 × navy, 1 × teal, 2 × white
• Row 5: 1 × white, 1 × teal, 1 × navy, 1 × light blue, 3 × navy, 1 × light blue, 1 × navy, 1 × teal, 2 × white
• Row 6: 1 × white, 1 × teal, 7 × navy, 1 × teal, 2 × white
• Row 7: 1 × white, 1 × teal, 2 × navy, 3 × light blue, 2 × navy, 1 × teal, 2 × white
• Row 8: 1 × white, 9 × teal, 2 × white
• Row 9: 3 × white, 4 × grey, 5 × white
• Row 10: 1 × white, 9 × yellow, 2 × white
• Row 11: 1 × white, 3 × yellow, 1 × white, 1 × pink, 1 × white, 3 × yellow, 2 × white
• Row 12: 1 × white, 9 × yellow, 2 × white