# 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 using colors created based on what they look like on-screen.

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.

## Notes

Dark colors have more precision in gamma-space sRGB than in linear-space RGB. Using this function to convert from sRGB to RGB can result in non-integer color values, which get truncated to integers and lose precision when used with other functions such as love.graphics.setColor.

## Examples

### Gamma-correct rendering using colored circles

    function love.load()
        -- Enable the sRGB mode for the window. This converts from linear RGB to gamma-space sRGB when
        -- things are drawn to the screen (but blending calculations are done in linear RGB space.)
        -- Computer monitors display in the sRGB color space.
        love.window.setMode(800, 600, {srgb=true, fsaa=4})

        -- If sRGB mode for the screen isn't supported, the flag will be false.
        local _, _, flags = love.window.getMode()
        gammacorrect = flags.srgb

        -- Here we have a red-ish color with 50% opacity. I chose the color values here based on what it looked like
        -- on-screen, and because computer monitors display in the sRGB color space, this color is in the sRGB color space.
        color1 = {187, 54, 100, 128}

        if gammacorrect then
            -- If the window is in srgb mode, it converts from linear RGB to sRGB when drawing. This means we need to
            -- convert the sRGB-space color to linear RGB space.
            color1 = {love.math.gammaToLinear(color1)}
        end

        -- We want this color to be halfway between white and black (with 50% opacity as well).
        -- If the window is in srgb mode, it expects linear-space colors and does blending that way, so this will work
        -- out fine. If the window isn't in srgb mode, the color won't be halfway between white and black because
        -- the values drawn to the screen aren't treated as linear-space RGB and converted to sRGB.
        -- We could use love.math.linearToGamma in that case, but blending would still be wrong.
        color2 = {128, 128, 128, 128}
    end

    -- Draw two overlapping circles with additive blending, using the colors above.
    function love.draw()
        love.graphics.setBlendMode("additive")

        love.graphics.setColor(color1)
        love.graphics.circle("fill", 300, 300, 200)

        love.graphics.setColor(color2)
        love.graphics.circle("fill", 500, 300, 200)
    end

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

    localfunction 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 'premultiplied' alpha blend mode.
    -- The multiplication correctly accounts for the color-space of the image.
    function NewPremultipliedImage(filepath, format)
        local imagedata = love.image.newImageData(filepath)

        local mapfunction = format == "srgb" and PremultiplyGammaPixel or PremultiplyLinearPixel
        imagedata:mapPixel(mapfunction)

        return love.graphics.newImage(imagedata, format)
    end

    -- This assumes gamma-correct rendering (with the sRGB window flag) is being done.
    image = NewPremultipliedImage("pig.png", "srgb")

## See Also

- love.math
- love.math.linearToGamma

##

Category:

- Functions