Exploring emoji encodings

Deep dive into Emoji encoding: from Unicode to UTF-8 bytes

Have you tried converting a string containing Emoji to bytes?

<code class="language-python">text = 'Hi ??‍♂️'

print(bytes(text, 'utf-8'))</code>

Output result:

<code>b'Hi \xf0\x9f\x99\x8b\xf0\x9f\x8f\xbd\xe2\x80\x8d\xe2\x99\x82\xef\xb8\x8f'</code>

Are you curious what those x are and how they convert back to Emoji?

Digging deeper, you will find that a single Emoji requires five Unicode characters to represent.

<code class="language-python">emoji = '??‍♂️'
print("Length: ", len(emoji))
for c in emoji:
    code = ord(c)
    print("{}\t{}\t{}".format(code, hex(code), c))</code>

Output result:

<code>Length:  5
128587  0x1f64b ?
127997  0x1f3fd ?
8205    0x200d  ‍
9794    0x2642  ♂
65039   0xfe0f  ️</code>

First, we have the basic emoji: Person with hands raised? (128587 or 0x1f64b in hexadecimal), usually represented as U 1F64B.

Then there’s the skin tone modifier: Light Skin Tone (127997).

Combine these two and you get a gender neutral raised hand person with this skin tone.

<code class="language-python">print(chr(128587) + chr(127997))</code>

Output result:

<code>??</code>

The penultimate character represents the male symbol, and the last character is called Variant Selector-16 (VS16), which indicates that the previous character should be displayed as an emoji, not a symbol.

Many characters can be displayed as symbols or emojis.

<code class="language-python">heart_symbol= '♥'
print(heart_symbol)
print(heart_symbol + chr(65039))</code>

Output result:

<code>♥
♥️</code>

Note: If the system or renderer does not support the emoji, it may be rendered as a symbol. In this case, copy the output and paste it into a different text editor or browser to see the differences.

Therefore, the first two and last two characters represent two separate Emoji expressions. The middle character is called a zero-width joiner (ZWJ) and is used to combine two or more emoji.

<code class="language-python">woman = '?'
laptop = '?'
print(woman + chr(8205) + laptop)</code>

Output result:

<code>?‍?</code>

Of course, the system or font must support these combinations, otherwise it will just render as separate characters.

<code class="language-python">man = '?'
toilet = '?'

print(man + chr(8205) + toilet)</code>

Output result:

<code>?‍?</code>

Now let’s see how each Unicode character is represented as bytes in UTF-8 encoding in general.

Let us consider the character U 1F64B.

First, we have to determine how many bytes are needed to store it based on the range of the character. We could store the number itself in just three bytes, but then there would be no way to decode it back to a single character. Therefore, the following pattern is used: (Why use this pattern?)

11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

Now let’s put the bits of the number 0x1f64b into this pattern. First convert it to binary.

<code class="language-python">print(bin(0x1F64B))</code>

Output result:

<code>0b11111011001001011</code>

The pattern has 21 bits, so let’s add 0 at the beginning to match:

000011111011001001011
000 011111 011001 001011

Put into pattern: 11110000 10011111 10011001 10001011

Now, what is the hexadecimal representation of these bytes?

<code class="language-python">print(list(map(hex, [0b11110000, 0b10011111, 0b10011001, 0b10001011])))</code>

Output result:

<code>['0xf0', '0x9f', '0x99', '0x8b']</code>

Note that these match the first four x we want to understand. Now you know what they mean.

Related notes: https://www.php.cn/link/0da44af358e8fcb6a6c2040602172d8d

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