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")

See Also

• love.math
• love.math.linearToGamma

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