image: add sixel image output to lui -a

This implements a stdimg for lui in console mode.
Images are sixel encoded and written to stdout, if they are not
assigned to a variable.

Example: A blue rectangle
	`img ⌶20 20⍴0xFF

Author: ktye

apl/eval.go

@@ -43,6 +43,15 @@ func (a *Apl) Eval(p Program) (err error) {
 				for e := range v[0] {
 					fmt.Fprintln(a.stdout, e.String(a))
 				}
+			case Image:
+				if a.stdimg != nil {
+					err = a.stdimg.WriteImage(v)
+					if err != nil {
+						return err
+					}
+				} else {
+					fmt.Println(a.stdout, v.String(a))
+				}
 			default:
 				fmt.Fprintln(a.stdout, val.String(a))
 			}

apl/image.go

@@ -108,7 +108,5 @@ func colorValue(c color.Color) Int {
 }
 func toColor(i int) color.Color {
 	u := uint32(i)
-	c := color.RGBA{uint8(u & 0xFF0000 >> 16), uint8(u & 0xFF00 >> 8), uint8(u & 0xFF), ^uint8(u >> 24)}
-	fmt.Println(c)
-	return c
+	return color.RGBA{uint8(u & 0xFF0000 >> 16), uint8(u & 0xFF00 >> 8), uint8(u & 0xFF), ^uint8(u >> 24)}
 }

aplextra/u/sixel.go

@@ -0,0 +1,20 @@
+package u
+
+import (
+	"io"
+
+	"github.com/ktye/iv/apl"
+	sixel "github.com/mattn/go-sixel"
+)
+
+// Sxl implements an apl.ImageWriter to serve as a stdimg device in a sixel capable terminal.
+type Sxl struct {
+	io.Writer
+}
+
+func (dev Sxl) WriteImage(m apl.Image) error {
+	// TODO animations
+
+	e := sixel.NewEncoder(dev.Writer)
+	return e.Encode(m.Im[0])
+}

cmd/lui/main.go

@@ -42,9 +42,12 @@ func main() {
 	case "-a":
 		a := newApl()
 		a.SetOutput(os.Stdout)
+		a.SetImage(u.Sxl{os.Stdout})
 		err = cmd.Apl(a, os.Stdin, os.Args[2:])
 	case "-i":
-		err = cmd.Iv(newApl(), strings.Join(os.Args[2:], " "), os.Stdout)
+		a := newApl()
+		a.SetImage(u.Sxl{os.Stdout})
+		err = cmd.Iv(a, strings.Join(os.Args[2:], " "), os.Stdout)
 	case "-z":
 		fmt.Println("TODO: attach zip file")
 	default: