SkLumaColorFilter Struct Reference

SkLumaColorFilter multiplies the luma of its input into the alpha channel, and sets the red, green, and blue channels to zero. More...

#include <SkLumaColorFilter.h>

Static Public Member Functions
static sk_sp< SkColorFilter >	Make ()

Detailed Description

SkLumaColorFilter multiplies the luma of its input into the alpha channel, and sets the red, green, and blue channels to zero.

SkLumaColorFilter(r,g,b,a) = {0,0,0, a * luma(r,g,b)}

This is similar to a luminanceToAlpha feColorMatrix, but note how this filter folds in the previous alpha, something an feColorMatrix cannot do.

feColorMatrix(luminanceToAlpha; r,g,b,a) = {0,0,0, luma(r,g,b)}

(Despite its name, an feColorMatrix using luminanceToAlpha does actually compute luma, a dot-product of gamma-encoded color channels, not luminance, a dot-product of linear color channels. So at least SkLumaColorFilter and feColorMatrix+luminanceToAlpha agree there.)

Member Function Documentation

Make()

static sk_sp<SkColorFilter> SkLumaColorFilter::Make ( )

static

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The documentation for this struct was generated from the following file:

• /CHECKOUT/include/effects/SkLumaColorFilter.h