Английская Википедия:Amiga Halfbrite mode

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Файл:32 vs Ehb64.png

Normal 32 color compares to an Extra Half Brite 64 color picture.

Файл:Ehb64.png

Extra Half Brite 64 color mode picture

Файл:32c.png

Normal 32 color mode picture

Extra Half Brite (also referred to as Extra-Half-Brite, Extra-Halfbrite, or EHB), is a planar display mode of the Amiga computer.

This mode uses six bitplanes (six bits per pixel). The first five bitplanes index 32 colors selected from a 12-bit color space of 4096 possible colors. If the bit on the sixth bitplane is set, the display hardware halves the brightness of the corresponding color component. This way 64 simultaneous colors are possible (32 arbitrary colors plus 32 half-bright components) while only using 32 color registers. The number of color registers is a hardware limitation of pre-AGA chipsets used in Amiga computers.

Some contemporary games (Fusion, Defender of the Crown, Agony, Lotus II, or Unreal) and animations (HalfBrite Hill) use EHB mode as a hardware-assisted means to display shadows or silhouettes. EHB is often used as general-purpose 64 color mode with the aforementioned restrictions.

Some early versions of the first Amiga, the Amiga 1000, sold in the United States, lack the EHB video mode, which is present in all later Amiga models.

See also

• Original Chip Set
• Hold-And-Modify

External links

• Animated demo using Halfbrite mode (requires Java)
• Amiga Graphics Archive - Extra Half-Brite