18 August 2020

8bit And 16bit Color Palettes

It took me quite a while to understand how 8bit and 16bit palettes work.

To spare you the search, I've decided to write this guide.


Motivation

Creating authentic 8bit and 16bit graphics requires understanding palettes. There are programs and algorithms, which transform your images into 8- or 16bit. Since algorithms cannot guess the intention behind the color choice and miss the context, creating them yourself is more flexible and results in higher quality. It also prevents the loss of details due to quantization. Additionally, to some, pixel-art is about control, and creating the palette gives such.


8Bit Graphics

During the era of the Nintendo Entertainment System, the technology worked with 8bit. Therefore the color of a pixel is represented by eight ones or zeroes. Today a pixel carries up to 32. You might be familiar with the red, green, and blue or RGB, where we split a color into three components. However, dividing 8bits into three colors is ambiguous. That's why there are formats for palettes. RGB332 is the most common for 8bit. It means we assign 3 bits to each red and green, and two bits to blue. A lighter orange would be 111 100 01, which would be 7 for red, 4 for green, and 1 for blue. That's nearly 0, so almost black.

comparisonBlackAndOrange
Comparing the colors.
Left: Black; Right: Our Orange


What Is A Palette

Better idea: We map each RGB value onto a level. 

For example, let's map the following blue levels:

00 -> 0

01 -> 79

10 -> 155

11 -> 255

The color levels (right-hand side) the bits map to is our palette. Back then, hardware limited us to use one palette for all drawn on the screen at the same time. Years later, the Super Nintendo Entertainment System was released. Powered by 16bit, our capabilities increased immensely! A typical format for 16bit is RGB565. Today we use 24bit ("true-color") and the RGB888 format. Some formats use RGBA, followed by four numbers, where A (="alpha") stands for the transparency.

Side note: The sum of the numbers does not need to add up to the number of available bits. Ergo RGB333 is a valid format for 16bits.


Creating A Palette From Colors

Using preexisting colors to create a palette takes three steps. First, choose a format. Then add them to your palette.

Let's use the following colors for an 8bit palette of the format RGB332:


Red
Green
Blue
Black   
000
Color 2
212211198
White  
255255255
Color 4
248216198
Color 5
248197198
Color 6
232173159
Color 7
979943
Color 8
11723473

The format gives us 3 bits for red and green and 2 bits for blue. The formula for the number of representable levels is 2bits. That is enough for 23 = 8 levels of red and green each and 22 = 4 levels of blue. However, our colors have six unique levels of blue (0, 43, 73, 159, 198, 255). Therefore we can't represent all eight colors.


Quantization

Quantization, the third step, will help us here. For this one, we'll merge close color levels.

Our two colors:

248 red, 216 green, 198 blue            232 red, 173 green, 159 blue

will then (for example) become:

248 red, 216 green, 198 blue            232 red, 173 green, 198 blue

By choosing a good looking and distinguishable color level, we can optimize this better than an algorithm. Then we continue adding all needed colors and quantify them to our palette. Now with our palette created, we can color the pixel art.


Tips And Tricks

Reminder: In 8bit and 16bit video games, everything on-screen at the same time uses one palette. Therefore use the same palette for all associated sprites.

The difference between darker colors is harder to notice. Thus use less dark color levels.


Examples


senkoPixelArt16Bit
Senko Pixel Art, 16Bit Palette (RGB565)
 drawn by GreenyNeko

This pixel art of Senko uses an RGB565 palette with the following color levels:

Color1234567891011121314151617...32
Red097126155174197205212222227232248----

Green04654608399106163173188197207211216224234255...-
Blue0434860738893101118159175198236255--



Notice that there's still space in the palette marked by the "-"s.

Senko Pixel Art, 8Bit Palette (RGB332)
drawn by GreenyNeko


This one uses an RGB332 palette with the following color levels:

Color12345678
Red097126155174197212248
Green4683106156173197216234
Blue43106175198


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I'm a junior game developer and software developer and I created this blog to share my ideas, thoughts and whatever I'm working on or doing.