blend: optimize a bit

blend/genblend.go

@@ -503,16 +503,16 @@ var draw{{.Name}}NRGBAToNRGBA drawFunc = func(dest []byte, src []byte, alpha uin
 {{end}}
 {{define "drawMain1_SrcRGBAToNRGBA"}}
 			if sa < 0xff {
-				sr = sr * 0xff / sa
-				sg = sg * 0xff / sa
-				sb = sb * 0xff / sa
+				sr = uint32(rgbaToNRGBATable[(sr<<8)+sa])
+				sg = uint32(rgbaToNRGBATable[(sg<<8)+sa])
+				sb = uint32(rgbaToNRGBATable[(sb<<8)+sa])
 			}
 {{end}}
 {{define "drawMain1_DestRGBAToNRGBA"}}
 			if 0x00 < da && da < 0xff {
-				dr = dr * 0xff / da
-				dg = dg * 0xff / da
-				db = db * 0xff / da
+				dr = uint32(rgbaToNRGBATable[(dr<<8)+da])
+				dg = uint32(rgbaToNRGBATable[(dg<<8)+da])
+				db = uint32(rgbaToNRGBATable[(db<<8)+da])
 			}
 {{end}}
 {{define "drawMain2"}}

blend/genporterduff.go

@@ -434,9 +434,9 @@ var draw{{.Name}}NRGBAToNRGBA drawFunc = func(dest []byte, src []byte, alpha uin
 				dpix[j+1] = 0
 				dpix[j+0] = 0
 			} else {
-				dpix[j+2] = uint8(b * 0xff / a)
-				dpix[j+1] = uint8(g * 0xff / a)
-				dpix[j+0] = uint8(r * 0xff / a)
+				dpix[j+2] = uint8(rgbaToNRGBATable[(b<<8)+a])
+				dpix[j+1] = uint8(rgbaToNRGBATable[(g<<8)+a])
+				dpix[j+0] = uint8(rgbaToNRGBATable[(r<<8)+a])
 			}
 {{end}}
 {{define "drawMain3"}}
@@ -557,9 +557,9 @@ var draw{{.Name}}AlphaToNRGBA drawFunc = func(dest []byte, src []byte, alpha uin
 				dpix[j+1] = 0
 				dpix[j+0] = 0
 			} else {
-				dpix[j+2] = uint8(b * 0xff / a)
-				dpix[j+1] = uint8(g * 0xff / a)
-				dpix[j+0] = uint8(r * 0xff / a)
+				dpix[j+2] = uint8(rgbaToNRGBATable[(b<<8)+a])
+				dpix[j+1] = uint8(rgbaToNRGBATable[(g<<8)+a])
+				dpix[j+0] = uint8(rgbaToNRGBATable[(r<<8)+a])
 			}
 {{end}}
 {{define "drawMainAlpha3"}}
@@ -645,9 +645,9 @@ var draw{{.Name}}UniformToNRGBA drawUniformFunc = func(dest []byte, sr, sg, sb,
 				dpix[j+1] = 0
 				dpix[j+0] = 0
 			} else {
-				dpix[j+2] = uint8(b * 0xff / a)
-				dpix[j+1] = uint8(g * 0xff / a)
-				dpix[j+0] = uint8(r * 0xff / a)
+				dpix[j+2] = uint8(rgbaToNRGBATable[(b<<8)+a])
+				dpix[j+1] = uint8(rgbaToNRGBATable[(g<<8)+a])
+				dpix[j+0] = uint8(rgbaToNRGBATable[(r<<8)+a])
 			}
 {{end}}
 {{define "drawMainUniform3"}}

blend/genrgba2nrgba.go

@@ -0,0 +1,49 @@
+// +build ignore
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"html/template"
+	"log"
+	"os"
+)
+
+var source = `// Code generated by genrgba2nrgba.go. DO NOT EDIT.
+package blend
+var rgbaToNRGBATable = [65536]uint16{
+	{{range $i, $v := .N}}{{printf "%s\n" $v}}{{end}}}
+`
+
+func main() {
+	t := template.Must(template.New("").Parse(source))
+
+	n := make([]string, 65536)
+	for i := 0; i < 256; i++ {
+		n[i<<8] = fmt.Sprintf("0, // %d * 255 / 0", i)
+		for j := 1; j < 256; j++ {
+			n[(i<<8)+j] = fmt.Sprintf("%d, // %d * 255 / %d", i*255/j, i, j)
+		}
+	}
+
+	b := bytes.NewBufferString("")
+	if err := t.Execute(b, map[string]interface{}{
+		"N": n,
+	}); err != nil {
+		log.Fatal(err)
+	}
+	buf, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	f, err := os.Create("zrgba2nrgbatable.go")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer f.Close()
+	if _, err = f.Write(buf); err != nil {
+		log.Fatal(err)
+	}
+}

blend/util.go

@@ -1,4 +1,5 @@
 //go:generate go run gendivtable.go
+//go:generate go run genrgba2nrgba.go
 //go:generate go run genblend.go
 //go:generate go run genporterduff.go