love.math.linearToGamma

Available since LÖVE 0.9.1

This function is not supported in earlier versions.

Converts a color from linear-space (RGB) to gamma-space (sRGB). This is useful when storing linear RGB color values in an image, because the linear RGB color space has less precision than sRGB for dark colors, which can result in noticeable color banding when drawing.

In general, colors chosen based on what they look like on-screen are already in gamma-space and should not be double-converted. Colors calculated using math are often in the linear RGB space.

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

cr, cg, cb = love.math.linearToGamma( lr, lg, lb )

Arguments

number lr

The red channel of the linear RGB color to convert.

number lg

The green channel of the linear RGB color to convert.

number lb

The blue channel of the linear RGB color to convert.

Returns

number cr

The red channel of the converted color in gamma sRGB space.

number cg

The green channel of the converted color in gamma sRGB space.

number cb

The blue channel of the converted color in gamma sRGB 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

cr, cg, cb = love.math.linearToGamma( color )

Arguments

table color

An array with the red, green, and blue channels of the linear RGB color to convert.

Returns

number cr

The red channel of the converted color in gamma sRGB space.

number cg

The green channel of the converted color in gamma sRGB space.

number cb

The blue channel of the converted color in gamma sRGB space.

Function

Synopsis

c = love.math.linearToGamma( lc )

Arguments

number lc

The value of a color channel in linear RGB space to convert.

Returns

number c

The value of the color channel in gamma sRGB 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.gammaToLinear

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