Issue #123 - Brightness Controls

[0xABADCAFE]

Adds controls for fine tuning the display brightness. Separate adjustments are provided for gamma, contrast and brightness offset.
These can be modified in game by using the numeric pad when not in map mode (map mode uses these for scrolling around the map).

• The brightness offset control effectively adjusts the black point.

  • NP 1 decreases
  • NP 2 resets to default
  • NP 3 increases

• The contrast control linearly adjusts the brightness scaling

  • NP 4 decreases
  • NP 5 resets to default
  • NP 6 increases

• The gamma control applies a precalculated gamma curve.

  • NP 7 decreases
  • NP 8 resets to default
  • NP 9 increases
  • For now the gamma adjustment is only capable of brightening

Notes:

• Settings are saved separately for AGA and RTG display types

• The actual implementation is a fixed point arithmetic equation of Lout = B + C * Lin ^ G applied to each gun of a palette entry when recalculating the palette:

  • Lin is the intensity input (0 - 1, represented as 0 - 255)
  • Lout is the intensity output (0 - 1, represented as 0 - 255)
  • B is the brightness adjustment as 8.8 fixed point
  • C is the contrast adjustment as 8.8 fixed point
  • G is the gamma (precalculated lookup for curves of x ^ 0.9375 - x ^ 0.5)

The current settings allow for some extreme modification and should be clamped accordingly.

The calculation is performed only when a setting changes and currently happens in Vid_the LoadMainPalette() which expects a 32-bit fractional value per gun.