Delete compose.go

compose.go

@@ -1,65 +0,0 @@
-package pixel
-
-import "errors"
-
-// ComposeTarget is a BasicTarget capable of Porter-Duff composition.
-type ComposeTarget interface {
-	BasicTarget
-
-	// SetComposeMethod sets a Porter-Duff composition method to be used.
-	SetComposeMethod(ComposeMethod)
-}
-
-// ComposeMethod is a Porter-Duff composition method.
-type ComposeMethod int
-
-// Here's the list of all available Porter-Duff composition methods. Use ComposeOver for the basic
-// alpha blending.
-const (
-	ComposeOver ComposeMethod = iota
-	ComposeIn
-	ComposeOut
-	ComposeAtop
-	ComposeRover
-	ComposeRin
-	ComposeRout
-	ComposeRatop
-	ComposeXor
-	ComposePlus
-	ComposeCopy
-)
-
-// Compose composes two colors together according to the ComposeMethod. A is the foreground, B is
-// the background.
-func (cm ComposeMethod) Compose(a, b RGBA) RGBA {
-	var fa, fb float64
-
-	switch cm {
-	case ComposeOver:
-		fa, fb = 1, 1-a.A
-	case ComposeIn:
-		fa, fb = b.A, 0
-	case ComposeOut:
-		fa, fb = 1-b.A, 0
-	case ComposeAtop:
-		fa, fb = b.A, 1-a.A
-	case ComposeRover:
-		fa, fb = 1-b.A, 1
-	case ComposeRin:
-		fa, fb = 0, a.A
-	case ComposeRout:
-		fa, fb = 0, 1-a.A
-	case ComposeRatop:
-		fa, fb = 1-b.A, a.A
-	case ComposeXor:
-		fa, fb = 1-b.A, 1-a.A
-	case ComposePlus:
-		fa, fb = 1, 1
-	case ComposeCopy:
-		fa, fb = 1, 0
-	default:
-		panic(errors.New("Compose: invalid ComposeMethod"))
-	}
-
-	return a.Mul(Alpha(fa)).Add(b.Mul(Alpha(fb)))
-}