bdf: make it possible to set the drawing colour

Intended for red and black tapes.

cmd/bdf-preview/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"html/template"
 	"image"
+	"image/color"
 	"image/draw"
 	"image/png"
 	"log"
@@ -82,7 +83,7 @@ func main() {
 
 		img := image.NewRGBA(super)
 		draw.Draw(img, super, image.White, image.ZP, draw.Src)
-		font.DrawString(img, image.ZP, font.Name)
+		font.DrawString(img, image.ZP, color.Black, font.Name)
 
 		fonts[filename] = fontItem{Font: font, Preview: img}
 	}

cmd/bdf-sample/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"image"
+	"image/color"
 	"image/draw"
 	"image/png"
 	"log"
@@ -26,7 +27,7 @@ func main() {
 
 	img := image.NewRGBA(super)
 	draw.Draw(img, super, image.White, image.ZP, draw.Src)
-	font.DrawString(img, image.ZP, font.Name)
+	font.DrawString(img, image.ZP, color.Black, font.Name)
 
 	fo, err := os.Create("out.png")
 	if err != nil {

cmd/label-tool/main.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"html/template"
 	"image"
+	"image/color"
 	"image/draw"
 	"image/png"
 	"log"
@@ -260,7 +261,7 @@ func main() {
 
 		img := image.NewRGBA(super)
 		draw.Draw(img, super, image.White, image.ZP, draw.Src)
-		font.DrawString(img, image.ZP, font.Name)
+		font.DrawString(img, image.ZP, color.Black, font.Name)
 
 		fonts = append(fonts, &fontItem{Path: path, Font: font, Preview: img})
 	}