Merging functions

Input type	Output type
color, color	color

The merging functions reproduce all layer merge modes. They accept two color parameters. The second color is merged onto the first color and the resulting color is returned. So, the first color is treated as the background, and the second color as the "layer" being merged. The alpha value of the result is always the alpha value of the second color.

The following functions are available:

mergenormal	Directly returns the second color.
mergemultiply	Multiplies the first color with the second color. The result is always a darker color.
mergescreen	Multiplies the inverse of the first color with the inverse of the second color, and returns the inverse of the result. This is always a lighter color.
mergeoverlay	Multiplies or screens the colors, depending on the first color.
mergehardlight	Multiplies or screens the colors, depending on the second color.
mergesoftlight	Darkens or lightens the colors, depending on the second color.
mergedarken	Returns the darkest of the two colors.
mergelighten	Returns the lightest of the two colors.
mergedifference	Returns the difference between the two colors.
mergehue	Returns the hue of the second color, and the saturation and luminance of the first color.
mergesaturation	Returns the saturation of the second color, and the hue and luminance of the first color.
mergecolor	Returns the hue and saturation of the second color, and the luminance of the first color.
mergeluminance	Returns the luminance of the second color, and the hue and saturation of the first color.
mergeaddition	Directly adds the two colors, limiting the result at white (1, 1, 1).
mergesubtraction	Directly subtracts the second color from the first color, limiting the result at black (0, 0, 0).
mergehsladdition	Adds the colors using the HSL color model.
mergered	Returns the red component of the second color, and the green and blue components of the first color.
mergegreen	Returns the green component of the second color, and the red and blue components of the first color.
mergeblue	Returns the blue component of the second color, and the red and green components of the first color.

With these functions, you can reproduce how layers are merged. Use the following formula to merge t on top of b with opacity o:

compose(b, blend(t, mergeX(b, t), alpha(b)), o)

The merging functions are often used as color user functions. See Parameter blocks.