use external color parser package

color.go

@@ -6,58 +6,19 @@
 package sm
 
 import (
-	"fmt"
 	"image/color"
-	"regexp"
-	"strings"
+
+	"github.com/mazznoer/csscolorparser"
 )
 
-// ParseColorString parses hex color strings (i.e. `0xRRGGBB`, `#RRGGBB`, `0xRRGGBBAA`, `#RRGGBBAA`), and names colors (e.g. 'black', 'blue', ...)
+// ParseColorString parses hex color strings (i.e. `#RRGGBB`, `RRGGBBAA`, `#RRGGBBAA`), and named colors (e.g. 'black', 'blue', ...)
 func ParseColorString(s string) (color.Color, error) {
-	s = strings.ToLower(strings.TrimSpace(s))
-
-	re := regexp.MustCompile(`^(0x|#)([A-Fa-f0-9]{6})$`)
-	matches := re.FindStringSubmatch(s)
-	if matches != nil {
-		var r, g, b int
-		fmt.Sscanf(matches[2], "%2x%2x%2x", &r, &g, &b)
-		return color.RGBA{uint8(r), uint8(g), uint8(b), 0xff}, nil
-	}
-
-	re = regexp.MustCompile(`^(0x|#)([A-Fa-f0-9]{8})$`)
-	matches = re.FindStringSubmatch(s)
-	if matches != nil {
-		var r, g, b, a int
-		fmt.Sscanf(matches[2], "%2x%2x%2x%2x", &r, &g, &b, &a)
-		rr := float64(r) * float64(a) / 256.0
-		gg := float64(g) * float64(a) / 256.0
-		bb := float64(b) * float64(a) / 256.0
-		return color.RGBA{uint8(rr), uint8(gg), uint8(bb), uint8(a)}, nil
-	}
-
-	switch s {
-	case "black":
-		return color.RGBA{0x00, 0x00, 0x00, 0xff}, nil
-	case "blue":
-		return color.RGBA{0x00, 0x00, 0xff, 0xff}, nil
-	case "brown":
-		return color.RGBA{0x96, 0x4b, 0x00, 0xff}, nil
-	case "green":
-		return color.RGBA{0x00, 0xff, 0x00, 0xff}, nil
-	case "orange":
-		return color.RGBA{0xff, 0x7f, 0x00, 0xff}, nil
-	case "purple":
-		return color.RGBA{0x7f, 0x00, 0x7f, 0xff}, nil
-	case "red":
-		return color.RGBA{0xff, 0x00, 0x00, 0xff}, nil
-	case "yellow":
-		return color.RGBA{0xff, 0xff, 0x00, 0xff}, nil
-	case "white":
-		return color.RGBA{0xff, 0xff, 0xff, 0xff}, nil
-	case "transparent":
-		return color.RGBA{0x00, 0x00, 0x00, 0x00}, nil
+	if col, err := csscolorparser.Parse(s); err != nil {
+		return nil, err
+	} else {
+		r, g, b, a := col.RGBA255()
+		return color.RGBA{r, g, b, a}, nil
 	}
-	return color.Transparent, fmt.Errorf("cannot parse color string '%s'", s)
 }
 
 // Luminance computes the luminance (~ brightness) of the given color. Range: 0.0 for black to 1.0 for white.

color_test.go

@@ -0,0 +1,47 @@
+package sm
+
+import (
+	"image/color"
+	"testing"
+)
+
+type string_color_err struct {
+	input          string
+	expected_color color.Color
+	expected_error bool
+}
+
+func TestParseColor(t *testing.T) {
+	for _, test := range []string_color_err{
+		{"WHITE", color.RGBA{0xFF, 0xFF, 0xFF, 0xFF}, false},
+		{"white", color.RGBA{0xFF, 0xFF, 0xFF, 0xFF}, false},
+		{"yellow", color.RGBA{0xFF, 0xFF, 0x00, 0xFF}, false},
+		{"transparent", color.RGBA{0x00, 0x00, 0x00, 0x00}, false},
+		{"#FF00FF42", color.RGBA{0xFF, 0x00, 0xFF, 0x42}, false},
+		{"#ff00ff42", color.RGBA{0xFF, 0x00, 0xFF, 0x42}, false},
+		{"#ff00ff", color.RGBA{0xFF, 0x00, 0xFF, 0xFF}, false},
+		{"#f0f", color.RGBA{0xFF, 0x00, 0xFF, 0xFF}, false},
+		{"FF00FF42", color.RGBA{0xFF, 0x00, 0xFF, 0x42}, false},
+		{"ff00ff42", color.RGBA{0xFF, 0x00, 0xFF, 0x42}, false},
+		{"ff00ff", color.RGBA{0xFF, 0x00, 0xFF, 0xFF}, false},
+		{"f0f", color.RGBA{0xFF, 0x00, 0xFF, 0xFF}, false},
+		{"bad-name", color.RGBA{0x00, 0x00, 0x00, 0x00}, true},
+		{"#FF00F", color.RGBA{0x00, 0x00, 0x00, 0x00}, true},
+		{"#GGGGGG", color.RGBA{0x00, 0x00, 0x00, 0x00}, true},
+		{"", color.RGBA{0x00, 0x00, 0x00, 0x00}, true},
+	} {
+		c, err := ParseColorString(test.input)
+		if test.expected_error {
+			if err == nil {
+				t.Errorf("error expected when parsing '%s'", test.input)
+			}
+		} else {
+			if err != nil {
+				t.Errorf("unexpected error when parsing '%s': %v", test.input, err)
+			}
+			if c != test.expected_color {
+				t.Errorf("unexpected color when parsing '%s': %v expected: %v", test.input, c, test.expected_color)
+			}
+		}
+	}
+}

go.mod

@@ -13,6 +13,7 @@ require (
 
 require (
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 // indirect
+	github.com/mazznoer/csscolorparser v0.1.3 // indirect
 	golang.org/x/net v0.22.0 // indirect
 	golang.org/x/sys v0.18.0 // indirect
 	golang.org/x/text v0.14.0 // indirect

go.sum

@@ -13,6 +13,8 @@ github.com/golang/geo v0.0.0-20230421003525-6adc56603217/go.mod h1:8wI0hitZ3a1Ix
 github.com/jessevdk/go-flags v1.5.0 h1:1jKYvbxEjfUl0fmqTCOfonvskHHXMjBySTLW4y9LFvc=
 github.com/jessevdk/go-flags v1.5.0/go.mod h1:Fw0T6WPc1dYxT4mKEZRfG5kJhaTDP9pj1c2EWnYs/m4=
 github.com/joeshaw/gengen v0.0.0-20190604015154-c77d87825f5a/go.mod h1:v2qvRL8Xwk4OlARK6gPlf2JreZXzv0dYp/8+kUJ0y7Q=
+github.com/mazznoer/csscolorparser v0.1.3 h1:vug4zh6loQxAUxfU1DZEu70gTPufDPspamZlHAkKcxE=
+github.com/mazznoer/csscolorparser v0.1.3/go.mod h1:Aj22+L/rYN/Y6bj3bYqO3N6g1dtdHtGfQ32xZ5PJQic=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=