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Amiga Halfbrite mode

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A normal 32 color image can be compared to an Extra Half Brite 64 color image.
Extra Half Brite 64 color mode picture
Normal 32 color mode picture

Extra Half Brite (also referred to as Extra-Half-Brite, Extra-Halfbrite, or EHB),[1][2][3][4] is a planar display mode of the Amiga computer.

This mode uses six bit planes (six bits per pixel).[3][5][6] The first five bit planes index 32 colors selected from a 12-bit color space of 4096 possible colors. If the bit on the sixth bit plane is set, the display hardware halves the brightness of the corresponding color component.[7] This way 64 simultaneous colors are possible (32 arbitrary colors plus 32 half-bright components) while using only 32 color registers.[8] The number of color registers is a hardware limitation of pre-AGA chipsets in Amiga computers.

Some contemporary games (Fusion,[9] Defender of the Crown,[10] Agony,[11] Lotus II,[12] or Unreal[13]) and animations (HalfBrite Hill[4]) use EHB mode as a hardware-assisted means to display shadows or silhouettes.[9][14] EHB is often used as general-purpose 64 color mode with its own restrictions.[9][15][16][17]

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.[4][2]

See also

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References

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  1. ^ Mortimore, Eugene P. (1986). Amiga Programmer's Handbook. SYBEX. ISBN 978-0-89588-343-8.
  2. ^ a b Maher, Jimmy (January 26, 2018). The Future Was Here: The Commodore Amiga. MIT Press. ISBN 978-0-262-53569-4.
  3. ^ a b "Amiga Hardware Reference Manual: Color Selection in Extra Half Brite (EHB) Mode". Amiga Developer Docs. Retrieved November 19, 2022.
  4. ^ a b c Sullivan, Kevin (1987). "HalfBrite Hill". Amiga Animations. Blair-Sullivan Computer Graphics & Animation. Retrieved November 19, 2022.
  5. ^ "The Atari ST and Amiga computing evolution!". Retroshowcase: oldschool game reference!. Retrieved November 19, 2022.
  6. ^ Peddie, Jon (June 8, 2022). "Amiga (1988)". IEEE Computer Society. Retrieved November 19, 2022.
  7. ^ Maher, Jimmy (January 26, 2018). The Future Was Here: The Commodore Amiga. MIT Press. ISBN 978-0-262-53569-4.
  8. ^ Amiga ROM Kernel Reference Manual: Libraries. Addison-Wesley. 1992. ISBN 978-0-201-56774-8.
  9. ^ a b c "Extra Half Bright (EHB)". Amiga Graphics Archive. Retrieved November 19, 2022.
  10. ^ "Defender of the Crown - Castle Norman - Amiga Graphics Archive". amiga.lychesis.net. Retrieved April 12, 2023.
  11. ^ "Agony - Loader 1 - Amiga Graphics Archive". amiga.lychesis.net. Retrieved April 12, 2023.
  12. ^ "Lotus 2 - Level 1 - Forest - Amiga Graphics Archive". amiga.lychesis.net. Retrieved April 12, 2023.
  13. ^ "Unreal - Amiga Graphics Archive". amiga.lychesis.net. Retrieved April 12, 2023.
  14. ^ "Enhanced Graphics - Extra Half-Brite (EHB) Mode". Hall Of Light - The database of Amiga games. Retrieved April 12, 2023.
  15. ^ "EHB images". Amiga Graphics Archive. Retrieved September 19, 2011.
  16. ^ Compute. Vol. 11. Small System Services. 1989. pp. 44, 53.
  17. ^ Kroah (2020). "The Bard's Tale serie - Bard's Tale Construction Set". Kroah's Game Reverse Engineering Page. Retrieved November 19, 2022.
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