love.math.gammaToLinear

Available since LÖVE 0.9.1
This function is not supported in earlier versions.

Converts a color from gamma-space (sRGB) to linear-space (RGB). This is useful when doing gamma-correct rendering and you need to do math in linear RGB in the few cases where LÖVE doesn't handle conversions automatically.

Read more about gamma-correct rendering here, here, and here.

Gamma-correct rendering is an advanced topic and it's easy to get color-spaces mixed up. If you're not sure whether you need this, you might want to avoid it.

Function

Synopsis

lr, lg, lb = love.math.gammaToLinear( r, g, b )

Arguments

number r: The red channel of the sRGB color to convert.
number g: The green channel of the sRGB color to convert.
number b: The blue channel of the sRGB color to convert.

Returns

number lr: The red channel of the converted color in linear RGB space.
number lg: The green channel of the converted color in linear RGB space.
number lb: The blue channel of the converted color in linear RGB space.

Notes

An alpha value can be passed into the function as a fourth argument, but it will be returned unchanged because alpha is always linear.

Function

Synopsis

lr, lg, lb = love.math.gammaToLinear( color )

Arguments

table color: An array with the red, green, and blue channels of the sRGB color to convert.

Returns

number lr: The red channel of the converted color in linear RGB space.
number lg: The green channel of the converted color in linear RGB space.
number lb: The blue channel of the converted color in linear RGB space.

Function

Synopsis

lc = love.math.gammaToLinear( c )

Arguments

number c: The value of a color channel in sRGB space to convert.

Returns

number lc: The value of the color channel in linear RGB space.

Examples

Pre-multiply an image's alpha with its RGB values in linear RGB space

local function PremultiplyLinearPixel(x, y, r, g, b, a)
   r = r * a / 255
   g = g * a / 255
   b = b * a / 255
   return r, g, b, a
end
 
local function PremultiplyGammaPixel(x, y, r, g, b, a)
   r, g, b = love.math.gammaToLinear(r, g, b)
   r = r * a / 255
   g = g * a / 255
   b = b * a / 255
   r, g, b = love.math.linearToGamma(r, g, b)
   return r, g, b, a
end
 
-- Loads an image and pre-multiplies its RGB values with its alpha, for use with the ('alpha', 'premultiplied') blend mode.
-- The multiplication correctly accounts for the color-space of the image.
function NewPremultipliedImage(filepath, flags)
    local imagedata = love.image.newImageData(filepath)
 
    local mapfunction = (flags and flags.linear) and PremultiplyLinearPixel or PremultiplyGammaPixel
    imagedata:mapPixel(mapfunction)
 
    return love.graphics.newImage(imagedata, flags)
end
 
image = NewPremultipliedImage("pig.png")

love.math.gammaToLinear