diff --git a/internal/f32color/rgba.go b/internal/f32color/rgba.go index d1b7564d..4fc27421 100644 --- a/internal/f32color/rgba.go +++ b/internal/f32color/rgba.go @@ -77,6 +77,40 @@ func NRGBAToRGBA(col color.NRGBA) color.RGBA { } } +// NRGBAToLinearRGBA converts from non-premultiplied sRGB color to premultiplied linear RGBA color. +// +// Each component in the result is `c * alpha`, where `c` is the linear color. +func NRGBAToLinearRGBA(col color.NRGBA) color.RGBA { + if col.A == 0xFF { + return color.RGBA(col) + } + c := LinearFromSRGB(col) + return color.RGBA{ + R: uint8(c.R*255 + .5), + G: uint8(c.G*255 + .5), + B: uint8(c.B*255 + .5), + A: col.A, + } +} + +// NRGBAToRGBA_PostAlpha converts from non-premultiplied sRGB color to premultiplied sRGB color. +// +// Each component in the result is `sRGBToLinear(c) * alpha`, where `c` +// is the linear color. +func NRGBAToRGBA_PostAlpha(col color.NRGBA) color.RGBA { + if col.A == 0xFF { + return color.RGBA(col) + } else if col.A == 0x00 { + return color.RGBA{} + } + return color.RGBA{ + R: uint8(uint32(col.R) * uint32(col.A) / 0xFF), + G: uint8(uint32(col.G) * uint32(col.A) / 0xFF), + B: uint8(uint32(col.B) * uint32(col.A) / 0xFF), + A: col.A, + } +} + // RGBAToNRGBA converts from premultiplied sRGB color to non-premultiplied sRGB color. func RGBAToNRGBA(col color.RGBA) color.NRGBA { if col.A == 0xFF { diff --git a/internal/f32color/rgba_test.go b/internal/f32color/rgba_test.go new file mode 100644 index 00000000..654fd139 --- /dev/null +++ b/internal/f32color/rgba_test.go @@ -0,0 +1,38 @@ +// SPDX-License-Identifier: Unlicense OR MIT + +package f32color + +import ( + "image/color" + "testing" +) + +func TestNRGBAToRGBA_PostAlpha_Boundary(t *testing.T) { + for col := 0; col <= 0xFF; col++ { + for alpha := 0; alpha <= 0xFF; alpha++ { + in := color.NRGBA{R: uint8(col), A: uint8(alpha)} + premul := NRGBAToRGBA_PostAlpha(in) + if premul.A != uint8(alpha) { + t.Errorf("%v: got %v expected %v", in, premul.A, alpha) + } + if premul.R > premul.A { + t.Errorf("%v: R=%v > A=%v", in, premul.R, premul.A) + } + } + } +} + +func TestNRGBAToLinearRGBA_Boundary(t *testing.T) { + for col := 0; col <= 0xFF; col++ { + for alpha := 0; alpha <= 0xFF; alpha++ { + in := color.NRGBA{R: uint8(col), A: uint8(alpha)} + premul := NRGBAToLinearRGBA(in) + if premul.A != uint8(alpha) { + t.Errorf("%v: got %v expected %v", in, premul.A, alpha) + } + if premul.R > premul.A { + t.Errorf("%v: R=%v > A=%v", in, premul.R, premul.A) + } + } + } +} diff --git a/widget/icon.go b/widget/icon.go index f6f88d3e..4e6350d8 100644 --- a/widget/icon.go +++ b/widget/icon.go @@ -51,7 +51,7 @@ func (ic *Icon) image(sz int) paint.ImageOp { img := image.NewRGBA(image.Rectangle{Max: image.Point{X: sz, Y: int(float32(sz) * dy / dx)}}) var ico iconvg.Rasterizer ico.SetDstImage(img, img.Bounds(), draw.Src) - m.Palette[0] = f32color.NRGBAToRGBA(ic.Color) + m.Palette[0] = f32color.NRGBAToLinearRGBA(ic.Color) iconvg.Decode(&ico, ic.src, &iconvg.DecodeOptions{ Palette: &m.Palette, }) diff --git a/widget/icon_test.go b/widget/icon_test.go new file mode 100644 index 00000000..dd927f7a --- /dev/null +++ b/widget/icon_test.go @@ -0,0 +1,30 @@ +// SPDX-License-Identifier: Unlicense OR MIT + +package widget + +import ( + "image" + "image/color" + "testing" + + "gioui.org/layout" + "gioui.org/op" + "gioui.org/unit" + "golang.org/x/exp/shiny/materialdesign/icons" +) + +func TestIcon_Alpha(t *testing.T) { + icon, err := NewIcon(icons.ToggleCheckBox) + if err != nil { + t.Fatal(err) + } + + icon.Color = color.NRGBA{B: 0xff, A: 0x40} + + gtx := layout.Context{ + Ops: new(op.Ops), + Constraints: layout.Exact(image.Pt(100, 100)), + } + + _ = icon.Layout(gtx, unit.Sp(18)) +}