colormath.h File Reference

SNES Color Math (Blending/Transparency) More...

#include <snes/types.h>

Go to the source code of this file.

Macros
#define	COLDATA_ALL   (COLDATA_RED | COLDATA_GREEN | COLDATA_BLUE)
	Apply fixed color to all channels.
#define	COLDATA_BLUE   0x80
	Apply fixed color to blue channel.
#define	COLDATA_GREEN   0x40
	Apply fixed color to green channel.
#define	COLDATA_RED   0x20
	Apply fixed color to red channel.
#define	COLORMATH_ADD   0
	Add colors (brightens)
#define	COLORMATH_ALL   0x3F
	Apply color math to all layers.
#define	COLORMATH_ALWAYS   0
	Always enable color math.
#define	COLORMATH_BACKDROP   BIT(5)
	Apply color math to backdrop (color 0)
#define	COLORMATH_BG1   BIT(0)
	Apply color math to BG1.
#define	COLORMATH_BG2   BIT(1)
	Apply color math to BG2.
#define	COLORMATH_BG3   BIT(2)
	Apply color math to BG3.
#define	COLORMATH_BG4   BIT(3)
	Apply color math to BG4.
#define	COLORMATH_INSIDE   1
	Enable inside window only.
#define	COLORMATH_NEVER   3
	Never enable color math.
#define	COLORMATH_OBJ   BIT(4)
	Apply color math to sprites (OBJ)
#define	COLORMATH_OUTSIDE   2
	Enable outside window only.
#define	COLORMATH_SRC_FIXED   1
	Use fixed color as color source.
#define	COLORMATH_SRC_SUBSCREEN   0
	Use sub screen as color source.
#define	COLORMATH_SUB   1
	Subtract colors (darkens)

Functions
void	colorMathDisable (void)
	Disable all color math.
void	colorMathEnable (u8 layers)
	Enable color math for specified layers.
void	colorMathInit (void)
	Initialize color math to defaults.
void	colorMathSetBrightness (u8 brightness)
	Set brightness for fade effects.
void	colorMathSetChannel (u8 channel, u8 intensity)
	Set a single fixed color channel.
void	colorMathSetCondition (u8 condition)
	Set when color math is enabled (window control)
void	colorMathSetFixedColor (u8 r, u8 g, u8 b)
	Set fixed color for blending.
void	colorMathSetHalf (u8 enable)
	Enable or disable half mode.
void	colorMathSetOp (u8 op)
	Set color math operation (add or subtract)
void	colorMathSetSource (u8 source)
	Set color math source.
void	colorMathShadow (u8 layers, u8 intensity)
	Set up shadow/darkening effect.
void	colorMathTint (u8 layers, u8 r, u8 g, u8 b)
	Set up color tint effect.
void	colorMathTransparency50 (u8 layers)
	Set up 50% transparency for layers.

Detailed Description

SNES Color Math (Blending/Transparency)

Color math enables blending between the main screen and sub screen or a fixed color. This creates effects like transparency, shadows, fading, and underwater tints.

How Color Math Works

The SNES can add or subtract colors:

• Add: Main screen + Sub screen (or fixed color) = brighter
• Subtract: Main screen - Sub screen (or fixed color) = darker

Half mode divides the result by 2, useful for 50% transparency.

Main Screen vs Sub Screen

• Main screen: Primary display (what you normally see)
• Sub screen: Secondary layer used for blending

For transparency, put the background on main screen and the transparent layer on sub screen.

Usage Example

// 50% transparent BG2 over BG1
REG_TM = TM_BG1 | TM_BG2;   // Both on main screen
REG_TS = TM_BG2;            // BG2 also on sub screen
 
colorMathEnable(COLORMATH_BG2);  // Apply math to BG2
colorMathSetOp(COLORMATH_ADD);   // Add mode
colorMathSetHalf(1);              // Divide by 2 = 50%
colorMathSetSource(COLORMATH_SRC_SUBSCREEN);  // Blend with sub screen

// Fade to black
colorMathSetFixedColor(0, 0, 0);  // Black
colorMathSetSource(COLORMATH_SRC_FIXED);
colorMathSetOp(COLORMATH_SUB);    // Subtract = darken
colorMathEnable(COLORMATH_ALL);   // Apply to all layers

Author

OpenSNES Team

Copyright

MIT License

Macro Definition Documentation

COLDATA_ALL

#define COLDATA_ALL   (COLDATA_RED | COLDATA_GREEN | COLDATA_BLUE)

Apply fixed color to all channels.

COLDATA_BLUE

#define COLDATA_BLUE   0x80

Apply fixed color to blue channel.

COLDATA_GREEN

#define COLDATA_GREEN   0x40

Apply fixed color to green channel.

COLDATA_RED

#define COLDATA_RED   0x20

Apply fixed color to red channel.

COLORMATH_ADD

#define COLORMATH_ADD   0

Add colors (brightens)

COLORMATH_ALL

#define COLORMATH_ALL   0x3F

Apply color math to all layers.

COLORMATH_ALWAYS

#define COLORMATH_ALWAYS   0

Always enable color math.

COLORMATH_BACKDROP

#define COLORMATH_BACKDROP   BIT(5)

Apply color math to backdrop (color 0)

COLORMATH_BG1

#define COLORMATH_BG1   BIT(0)

Apply color math to BG1.

COLORMATH_BG2

#define COLORMATH_BG2   BIT(1)

Apply color math to BG2.

COLORMATH_BG3

#define COLORMATH_BG3   BIT(2)

Apply color math to BG3.

COLORMATH_BG4

#define COLORMATH_BG4   BIT(3)

Apply color math to BG4.

COLORMATH_INSIDE

#define COLORMATH_INSIDE   1

Enable inside window only.

COLORMATH_NEVER

#define COLORMATH_NEVER   3

Never enable color math.

COLORMATH_OBJ

#define COLORMATH_OBJ   BIT(4)

Apply color math to sprites (OBJ)

COLORMATH_OUTSIDE

#define COLORMATH_OUTSIDE   2

Enable outside window only.

COLORMATH_SRC_FIXED

#define COLORMATH_SRC_FIXED   1

Use fixed color as color source.

COLORMATH_SRC_SUBSCREEN

#define COLORMATH_SRC_SUBSCREEN   0

Use sub screen as color source.

COLORMATH_SUB

#define COLORMATH_SUB   1

Subtract colors (darkens)

Function Documentation

colorMathDisable()

void colorMathDisable

(

void

)

Disable all color math.

colorMathEnable()

void colorMathEnable

(

u8

layers

)

Enable color math for specified layers.

Enables color math blending for the given layers.

Parameters

layers

Layer mask (COLORMATH_BG1, COLORMATH_BG2, etc.)

colorMathInit()

void colorMathInit

(

void

)

Initialize color math to defaults.

Disables all color math effects.

colorMathSetBrightness()

void colorMathSetBrightness

(

u8

brightness

)

Set brightness for fade effects.

Sets the fixed color for use in fading. Use with colorMathSetOp() to fade to white (add) or black (subtract).

Parameters

brightness

Fade level (0 = no effect, 31 = full white/black)

colorMathSetChannel()

void colorMathSetChannel	(	u8	channel,
		u8	intensity
	)

Set a single fixed color channel.

Parameters

channel	Channel mask (COLDATA_RED, COLDATA_GREEN, COLDATA_BLUE)
intensity	Intensity (0-31)

colorMathSetCondition()

void colorMathSetCondition

(

u8

condition

)

Set when color math is enabled (window control)

Parameters

condition

COLORMATH_ALWAYS, COLORMATH_INSIDE, COLORMATH_OUTSIDE, or COLORMATH_NEVER

colorMathSetFixedColor()

void colorMathSetFixedColor	(	u8	r,
		u8	g,
		u8	b
	)

Set fixed color for blending.

Sets the fixed color used when source is COLORMATH_SRC_FIXED.

Parameters

r	Red intensity (0-31)
g	Green intensity (0-31)
b	Blue intensity (0-31)

colorMathSetHalf()

void colorMathSetHalf

(

u8

enable

)

Enable or disable half mode.

When enabled, the color math result is divided by 2. This creates 50% transparency/blending.

Parameters

enable

1 = divide by 2, 0 = full result

colorMathSetOp()

void colorMathSetOp

(

u8

op

)

Set color math operation (add or subtract)

Parameters

op	Operation (COLORMATH_ADD or COLORMATH_SUB)

colorMathSetSource()

void colorMathSetSource

(

u8

source

)

Set color math source.

Chooses whether to blend with the sub screen or a fixed color.

Parameters

source

COLORMATH_SRC_SUBSCREEN or COLORMATH_SRC_FIXED

colorMathShadow()

void colorMathShadow	(	u8	layers,
		u8	intensity
	)

Set up shadow/darkening effect.

Subtracts fixed color from layers to darken them.

Parameters

layers	Layers to darken
intensity	Darkness level (0-31, higher = darker)

colorMathTint()

void colorMathTint	(	u8	layers,
		u8	r,
		u8	g,
		u8	b
	)

Set up color tint effect.

Adds a fixed color tint to layers.

Parameters

layers	Layers to tint
r	Red tint (0-31)
g	Green tint (0-31)
b	Blue tint (0-31)

colorMathTransparency50()

void colorMathTransparency50

(

u8

layers

)

Set up 50% transparency for layers.

Quick setup for semi-transparent layers. The transparent layers should be on both main and sub screen.

Parameters

layers

Layers to make 50% transparent

Note

You must also set REG_TS to include the transparent layers