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all: use color.NRGBA in public API

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color.RGBA has two problems with regards to using it.

First the color values need to be premultiplied, whereas most APIs
have non-premultiplied values. This is mainly to preserve color components
with low alpha values.

Second there are two ways to premultiply with sRGB. One is to premultiply
after sRGB conversion, the other is before. This makes using the API more
confusing.

Using color.NRGBA in sRGB makes it align with CSS.e

Signed-off-by: Egon Elbre <egonelbre@gmail.com>
This commit is contained in:
Egon Elbre
2020-11-18 20:21:26 +02:00
committed by Elias Naur
parent 9469d18907
commit 21ef492cc9
23 changed files with 200 additions and 157 deletions
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app/headless/backend_test.go
+20 -19
View File
@@ -19,15 +19,16 @@ import (
var dumpImages = flag.Bool("saveimages", false, "save test images")
var clearCol = color.RGBA{A: 0xff, R: 0xde, G: 0xad, B: 0xbe}
var clearCol = color.NRGBA{A: 0xff, R: 0xde, G: 0xad, B: 0xbe}
var clearColExpect = f32color.NRGBAToRGBA(clearCol)
func TestFramebufferClear(t *testing.T) {
b := newBackend(t)
sz := image.Point{X: 800, Y: 600}
fbo := setupFBO(t, b, sz)
img := screenshot(t, fbo, sz)
if got := img.RGBAAt(0, 0); got != clearCol {
t.Errorf("got color %v, expected %v", got, clearCol)
if got := img.RGBAAt(0, 0); got != clearColExpect {
t.Errorf("got color %v, expected %v", got, clearColExpect)
}
}
@@ -43,14 +44,14 @@ func TestSimpleShader(t *testing.T) {
b.BindProgram(p)
b.DrawArrays(backend.DrawModeTriangles, 0, 3)
img := screenshot(t, fbo, sz)
if got := img.RGBAAt(0, 0); got != clearCol {
t.Errorf("got color %v, expected %v", got, clearCol)
if got := img.RGBAAt(0, 0); got != clearColExpect {
t.Errorf("got color %v, expected %v", got, clearColExpect)
}
// Just off the center to catch inverted triangles.
cx, cy := 300, 400
shaderCol := f32color.RGBA{R: .25, G: .55, B: .75, A: 1.0}
if got, exp := img.RGBAAt(cx, cy), shaderCol.SRGB(); got != exp {
t.Errorf("got color %v, expected %v", got, exp)
if got, exp := img.RGBAAt(cx, cy), shaderCol.SRGB(); got != f32color.NRGBAToRGBA(exp) {
t.Errorf("got color %v, expected %v", got, f32color.NRGBAToRGBA(exp))
}
}
@@ -90,13 +91,13 @@ func TestInputShader(t *testing.T) {
b.BindInputLayout(layout)
b.DrawArrays(backend.DrawModeTriangles, 0, 3)
img := screenshot(t, fbo, sz)
if got := img.RGBAAt(0, 0); got != clearCol {
t.Errorf("got color %v, expected %v", got, clearCol)
if got := img.RGBAAt(0, 0); got != clearColExpect {
t.Errorf("got color %v, expected %v", got, clearColExpect)
}
cx, cy := 300, 400
shaderCol := f32color.RGBA{R: .25, G: .55, B: .75, A: 1.0}
if got, exp := img.RGBAAt(cx, cy), shaderCol.SRGB(); got != exp {
t.Errorf("got color %v, expected %v", got, exp)
if got, exp := img.RGBAAt(cx, cy), shaderCol.SRGB(); got != f32color.NRGBAToRGBA(exp) {
t.Errorf("got color %v, expected %v", got, f32color.NRGBAToRGBA(exp))
}
}
@@ -106,21 +107,21 @@ func TestFramebuffers(t *testing.T) {
fbo1 := newFBO(t, b, sz)
fbo2 := newFBO(t, b, sz)
var (
col1 = color.RGBA{R: 0xad, G: 0xbe, B: 0xef, A: 0xde}
col2 = color.RGBA{R: 0xfe, G: 0xba, B: 0xbe, A: 0xca}
col1 = color.NRGBA{R: 0xad, G: 0xbe, B: 0xef, A: 0xde}
col2 = color.NRGBA{R: 0xfe, G: 0xba, B: 0xbe, A: 0xca}
)
fcol1, fcol2 := f32color.RGBAFromSRGB(col1), f32color.RGBAFromSRGB(col2)
fcol1, fcol2 := f32color.LinearFromSRGB(col1), f32color.LinearFromSRGB(col2)
b.BindFramebuffer(fbo1)
b.Clear(fcol1.Float32())
b.BindFramebuffer(fbo2)
b.Clear(fcol2.Float32())
img := screenshot(t, fbo1, sz)
if got := img.RGBAAt(0, 0); got != col1 {
t.Errorf("got color %v, expected %v", got, col1)
if got := img.RGBAAt(0, 0); got != f32color.NRGBAToRGBA(col1) {
t.Errorf("got color %v, expected %v", got, f32color.NRGBAToRGBA(col1))
}
img = screenshot(t, fbo2, sz)
if got := img.RGBAAt(0, 0); got != col2 {
t.Errorf("got color %v, expected %v", got, col2)
if got := img.RGBAAt(0, 0); got != f32color.NRGBAToRGBA(col2) {
t.Errorf("got color %v, expected %v", got, f32color.NRGBAToRGBA(col2))
}
}
@@ -129,7 +130,7 @@ func setupFBO(t *testing.T, b backend.Device, size image.Point) backend.Framebuf
b.BindFramebuffer(fbo)
// ClearColor accepts linear RGBA colors, while 8-bit colors
// are in the sRGB color space.
col := f32color.RGBAFromSRGB(clearCol)
col := f32color.LinearFromSRGB(clearCol)
b.Clear(col.Float32())
b.ClearDepth(0.0)
b.Viewport(0, 0, size.X, size.Y)