bdf: make it possible to set the drawing colour

Intended for red and black tapes.

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2019, Přemysl Eric Janouch <p@janouch.name>
+Copyright (c) 2019 - 2021, Přemysl Eric Janouch <p@janouch.name>
 
 Permission to use, copy, modify, and/or distribute this software for any
 purpose with or without fee is hereby granted.

bdf/bdf.go

@@ -66,11 +66,13 @@ func (f *Font) FindGlyph(r rune) (glyph, bool) {
 
 // DrawString draws the specified text string onto dst horizontally along
 // the baseline starting at dp, using black color.
-func (f *Font) DrawString(dst draw.Image, dp image.Point, s string) {
+func (f *Font) DrawString(dst draw.Image, dp image.Point,
+	color color.Color, s string) {
+	src := image.NewUniform(color)
 	for _, r := range s {
 		g, _ := f.FindGlyph(r)
 		draw.DrawMask(dst, g.bounds.Add(dp),
-			image.Black, image.ZP, &g, g.bounds.Min, draw.Over)
+			src, image.ZP, &g, g.bounds.Min, draw.Over)
 		dp.X += g.advance
 	}
 }

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})
 	}

label/label.go

@@ -2,6 +2,7 @@ package label
 
 import (
 	"image"
+	"image/color"
 	"image/draw"
 	"strings"
 
@@ -19,7 +20,7 @@ func GenLabelForHeight(font *bdf.Font,
 	textRect, _ := font.BoundString(text)
 	textImg := image.NewRGBA(textRect)
 	draw.Draw(textImg, textRect, image.White, image.ZP, draw.Src)
-	font.DrawString(textImg, image.ZP, text)
+	font.DrawString(textImg, image.ZP, color.Black, text)
 
 	scaledTextImg := imgutil.Scale{Image: textImg, Scale: scale}
 	scaledTextRect := scaledTextImg.Bounds()
@@ -93,7 +94,7 @@ func GenLabelForWidth(font *bdf.Font,
 	for i, line := range lines {
 		textImg := image.NewRGBA(rects[i])
 		draw.Draw(textImg, rects[i], image.White, image.ZP, draw.Src)
-		font.DrawString(textImg, image.ZP, line)
+		font.DrawString(textImg, image.ZP, color.Black, line)
 
 		scaledImg := imgutil.Scale{Image: textImg, Scale: scale}
 		scaledRect := scaledImg.Bounds()