Handling of palettes. More...

#include "stdafx.h"
#include "blitter/base.hpp"
#include "blitter/factory.hpp"
#include "fileio_func.h"
#include "gfx_type.h"
#include "landscape_type.h"
#include "palette_func.h"
#include "settings_type.h"
#include "thread.h"
#include "table/palettes.h"
#include "safeguards.h"

Data Structures
struct	ColourGradients
	Lookup table of colour shades for all 16 colour gradients. More...

Macros
#define	EXTR(p, q) (((uint16_t)(palette_animation_counter * (p)) * (q)) >> 16)

#define	EXTR2(p, q) (((uint16_t)(~palette_animation_counter * (p)) * (q)) >> 16)

Typedefs
using	PaletteLookup = std::array< uint8_t, 1U<<(PALETTE_BITS *3)>

Functions
uint	CrunchColour (uint c)
	Reduce bits per channel to PALETTE_BITS, and place value in the middle of the reduced range. More...

static uint	CalculateColourDistance (const Colour &col1, int r2, int g2, int b2)
	Calculate distance between two colours. More...

static uint8_t	FindNearestColourIndex (uint8_t r, uint8_t g, uint8_t b)
	Find nearest colour palette index for a 32bpp pixel. More...

uint8_t	GetNearestColourIndex (uint8_t r, uint8_t g, uint8_t b)
	Get nearest colour palette index from an RGB colour. More...

void	DoPaletteAnimations ()

void	GfxInitPalettes ()

bool	CopyPalette (Palette &local_palette, bool force_copy)
	Copy the current palette if the palette was updated. More...

TextColour	GetContrastColour (uint8_t background, uint8_t threshold)
	Determine a contrasty text colour for a coloured background. More...

uint8_t	GetColourGradient (Colours colour, ColourShade shade)
	Get colour gradient palette index. More...

void	SetColourGradient (Colours colour, ColourShade shade, uint8_t palette_index)
	Set colour gradient palette index. More...

Variables
Palette	_cur_palette
	Current palette.

static std::recursive_mutex	_palette_mutex
	To coordinate access to _cur_palette.

const uint	PALETTE_BITS = 6
	PALETTE_BITS reduces the bits-per-channel of 32bpp graphics data to allow faster palette lookups from a smaller lookup table. More...

const uint	PALETTE_SHIFT = 8 - PALETTE_BITS

const uint	PALETTE_BITS_MASK = ((1U << PALETTE_BITS) - 1) << PALETTE_SHIFT

const uint	PALETTE_BITS_OR = (1U << (PALETTE_SHIFT - 1))

static PaletteLookup	_palette_lookup {}

const uint8_t	PALETTE_INDEX_CC_START = 198
	Palette index of start of company colour remap area.

const uint8_t	PALETTE_INDEX_CC_END = PALETTE_INDEX_CC_START + 8
	Palette index of end of company colour remap area.

const uint8_t	PALETTE_INDEX_START = 1
	Palette index of start of defined palette.

const uint8_t	PALETTE_INDEX_END = 215
	Palette index of end of defined palette.

Detailed Description

Handling of palettes.

Definition in file palette.cpp.

Function Documentation

◆ CalculateColourDistance()

static uint CalculateColourDistance	(	const Colour &	col1,
		int	r2,
		int	g2,
		int	b2
	)

static

Calculate distance between two colours.

Parameters

col1	First colour.
r2	Red component of second colour.
g2	Green component of second colour.
b2	Blue component of second colour.

Returns: Euclidean distance between first and second colour.

Definition at line 70 of file palette.cpp.

Referenced by FindNearestColourIndex().

◆ CopyPalette()

bool CopyPalette	(	Palette &	local_palette,
		bool	force_copy
	)

Copy the current palette if the palette was updated.

Used by video-driver to get a current up-to-date version of the palette, to avoid two threads accessing the same piece of memory (with a good chance one is already updating the palette while the other is drawing based on it).

Parameters

local_palette	The location to copy the palette to.
force_copy	Whether to ignore if there is an update for the palette.

Returns: True iff a copy was done.

Definition at line 152 of file palette.cpp.

References _cur_palette, _palette_mutex, Palette::count_dirty, Palette::first_dirty, and lock.

Referenced by VideoDriver_SDL_Base::CheckPaletteAnim(), VideoDriver_SDL::CheckPaletteAnim(), VideoDriver_Win32Base::CheckPaletteAnim(), and VideoDriver_SDL_Base::ClientSizeChanged().

◆ CrunchColour()

uint CrunchColour ( uint c )

inline

Reduce bits per channel to PALETTE_BITS, and place value in the middle of the reduced range.

This is to counteract the information lost between bright and dark pixels, e.g if PALETTE_BITS was 2: 0 - 63 -> 32 64 - 127 -> 96 128 - 191 -> 160 192 - 255 -> 224

Parameters

c	8 bit colour component.

Returns: Colour component reduced to PALETTE_BITS.

Definition at line 57 of file palette.cpp.

Referenced by FindNearestColourIndex().

◆ FindNearestColourIndex()

static uint8_t FindNearestColourIndex	(	uint8_t	r,
		uint8_t	g,
		uint8_t	b
	)

static

Find nearest colour palette index for a 32bpp pixel.

Parameters

r	Red component.
g	Green component.
b	Blue component.

Returns: palette index of nearest colour.

Definition at line 94 of file palette.cpp.

References _palette, CalculateColourDistance(), CrunchColour(), Palette::palette, PALETTE_INDEX_CC_END, PALETTE_INDEX_CC_START, PALETTE_INDEX_END, and PALETTE_INDEX_START.

◆ GetColourGradient()

uint8_t GetColourGradient	(	Colours	colour,
		ColourShade	shade
	)

Get colour gradient palette index.

Parameters

colour	Colour.
shade	Shade level from 1 to 7.

Returns: palette index of colour.

Definition at line 314 of file palette.cpp.

Referenced by NWidgetMatrix::Draw(), DrawCaption(), DrawFrame(), LinkGraphOverlay::DrawStationDots(), and GetDrawStringCompanyColour().

◆ GetContrastColour()

TextColour GetContrastColour	(	uint8_t	background,
		uint8_t	threshold
	)

Determine a contrasty text colour for a coloured background.

Parameters

background	Background colour.
threshold	Background colour brightness threshold below which the background is considered dark and TC_WHITE is returned, range: 0 - 255, default 128.

Returns: TC_BLACK or TC_WHITE depending on what gives a better contrast.

Definition at line 287 of file palette.cpp.

References _cur_palette, and Palette::palette.

◆ GetNearestColourIndex()

uint8_t GetNearestColourIndex	(	uint8_t	r,
		uint8_t	g,
		uint8_t	b
	)

Get nearest colour palette index from an RGB colour.

A search is performed if this colour is not already in the lookup table.

Parameters

r	Red component.
g	Green component.
b	Blue component.

Returns: nearest colour palette index.

Definition at line 127 of file palette.cpp.

◆ SetColourGradient()

void SetColourGradient	(	Colours	colour,
		ColourShade	shade,
		uint8_t	palette_index
	)

Set colour gradient palette index.

Parameters

colour	Colour.
shade	Shade level from 1 to 7.
palette_index	Palette index to set.

Definition at line 325 of file palette.cpp.

Variable Documentation

◆ PALETTE_BITS

const uint PALETTE_BITS = 6

PALETTE_BITS reduces the bits-per-channel of 32bpp graphics data to allow faster palette lookups from a smaller lookup table.

6 bpc is chosen as this results in a palette lookup table of 256KiB with adequate fidelty. In constract, a 5 bpc lookup table would be 32KiB, and 7 bpc would be 2MiB.

Values in the table are filled as they are first encountered – larger lookup table means more colour distance calculations, and is therefore slower.

Definition at line 38 of file palette.cpp.

Data Structures

Macros

Typedefs

Functions

Variables

Detailed Description

Function Documentation

◆ CalculateColourDistance()

◆ CopyPalette()

◆ CrunchColour()

◆ FindNearestColourIndex()

◆ GetColourGradient()

◆ GetContrastColour()

◆ GetNearestColourIndex()

◆ SetColourGradient()

Variable Documentation

◆ PALETTE_BITS