Display/Palette

The display system provides sixteen different palettes that can be used to color or shade tiles.

• Palettes 0-7 can be used for the two screens only;
• Palettes 8-15 can be used for both screens and sprites.

Palette format

Mono

In mono modes, palettes are stored in I/O ports 0x20 through 0x3F. Each palette contains four three-bit entries, which are pointers into a global, four-bit shade lookup table:

      Palette            Global shade LUT
 1  ===========> 2 ==========================> 5
 ^  (0, 2, 4, 6) ^ (1, 3, 5, 7, 9, 11, 13, 15) ^
 |               |                             |
Palette index   Value                         Displayed shade

The shade value corresponds to the darkness of the pixel: shade 0 is the brightest, while shade 15 is the darkest.

Color

In color modes, palettes are stored as 16-bit words in memory addresses 0xFE00 through 0xFFFF, without additional lookup tables:

       Address
15  bit  8  7  bit  0
 ---- ----  ---- ----
 1111 111p  pppi iii.
         |  |||| |||
         |  |||+-+++-- Index in palette (0-15)
         +--+++------- Palette number (0-15)

         Data
15  bit  8  7  bit  0
 ---- ----  ---- ----
 .... rrrr  gggg bbbb
      ||||  |||| ||||
      ||||  |||| ++++- Blue (0-15)
      ||||  ++++------ Green (0-15)
      ++++------------ Red (0-15)

In 2 bits per pixel color modes, palette entries 4 through 15 are not used.

Palette transparency

In two bit per pixel modes:

• Palettes 0-3 and 8-11 are opaque. For these, index zero is treated as opaque.
• Palettes 4-7 and 12-15 are translucent. For these, index zero is treated as transparent. This means that the color/shade value set to it is ignored, and only three distinct colors/shades can be used for tiles.

In four bit per pixel modes, all palettes are translucent. Index zero is always treated as transparent, and fifteen different colors/shades can be used for tiles.

Color reproduction

Different variants of the WonderSwan have displays which reproduce colors differently. As such, there is no canon palette for the system.

WonderSwan "mono"

This model uses an FSTN display with an approximately linear gamma (~1.0) response for the shades 0 (brightest) through 15 (darkest). Its color reproduction characteristics are very similar to Nintendo's Game Boy Pocket, which uses the same technology.

WonderSwan Color

This model uses a CSTN display.

In "mono" compatibility mode on Color consoles, the linear gamma response is not retained; shade 0 is equivalent to color #FFF, shade 1 to #EEE, and shade 15 is equivalent to color #000

SwanCrystal

This model uses a TFT LCD display. Its color reproduction characteristics are very similar to Nintendo's Game Boy Color, which uses the same technology. Its gamma is close to standard video (2.2).

Aftermarket/non-standard hardware

Generally, IPS mods, as well as both official and unofficial TV output kits, use standard video gamma throughout, even for the "mono" WonderSwan.