fix(misc): improve wheel beta label readability

internal/modules/misc/handlers_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"image"
+	"image/color"
 	"image/gif"
 	"math"
 	"math/rand/v2"
@@ -12,6 +13,7 @@ import (
 	"time"
 
 	"github.com/go-telegram/bot/models"
+	"golang.org/x/image/font/sfnt"
 
 	"github.com/tiennm99/miti99bot/internal/modules"
 	"github.com/tiennm99/miti99bot/internal/storage"
@@ -425,6 +427,25 @@ func TestWheelOfNamesBeta_RotatesOptionLabelsWithSlices(t *testing.T) {
 	}
 }
 
+func TestWheelOfNamesBeta_RotatedLabelIgnoresFaintMaskPixels(t *testing.T) {
+	img := image.NewPaletted(image.Rect(0, 0, 7, 7), wheelBetaPalette)
+	mask := image.NewAlpha(image.Rect(0, 0, 3, 1))
+	mask.SetAlpha(0, 0, color.Alpha{A: wheelBetaSliceLabelAlphaThreshold - 1})
+	mask.SetAlpha(1, 0, color.Alpha{A: wheelBetaSliceLabelAlphaThreshold})
+	mask.SetAlpha(2, 0, color.Alpha{A: 255})
+
+	stampRotatedTextMask(img, mask, 3, 3, 0, wheelBetaInkColorIndex, wheelBetaSliceLabelAlphaThreshold)
+
+	if got := img.ColorIndexAt(2, 3); got == wheelBetaInkColorIndex {
+		t.Fatalf("faint mask pixel became ink color %d", got)
+	}
+	for _, x := range []int{3, 4} {
+		if got := img.ColorIndexAt(x, 3); got != wheelBetaInkColorIndex {
+			t.Fatalf("strong mask pixel at x=%d color = %d, want ink color %d", x, got, wheelBetaInkColorIndex)
+		}
+	}
+}
+
 func TestWheelOfNamesBeta_DisplayTextPreservesVietnamese(t *testing.T) {
 	input := "Tiếng Việt Đặng"
 	got := wheelBetaDisplayText(input, 32)
@@ -436,6 +457,20 @@ func TestWheelOfNamesBeta_DisplayTextPreservesVietnamese(t *testing.T) {
 	}
 }
 
+func TestWheelOfNamesBeta_FontUsesNormalWeight(t *testing.T) {
+	subfamily, err := wheelBetaTextFont.Name(nil, sfnt.NameIDSubfamily)
+	if err != nil {
+		t.Fatalf("font subfamily: %v", err)
+	}
+	normalized := strings.ToLower(subfamily)
+	if strings.Contains(normalized, "bold") {
+		t.Fatalf("font subfamily = %q, want normal non-bold face", subfamily)
+	}
+	if normalized != "book" && normalized != "regular" {
+		t.Fatalf("font subfamily = %q, want normal face such as Book or Regular", subfamily)
+	}
+}
+
 func TestWheelOfNamesBeta_FontSupportsVietnameseGlyphs(t *testing.T) {
 	for _, r := range "Tiếng Việt Đặng Ơ Ư ấ ệ" {
 		if r == ' ' {

internal/modules/misc/wheelofnames_beta_drawing.go

@@ -14,9 +14,10 @@ import (
 )
 
 const (
-	wheelBetaSliceLabelRadius = 64
-	wheelBetaFontSize         = 10
-	wheelBetaFontDPI          = 72
+	wheelBetaSliceLabelRadius         = 64
+	wheelBetaSliceLabelAlphaThreshold = 96
+	wheelBetaFontSize                 = 10
+	wheelBetaFontDPI                  = 72
 )
 
 //go:embed fonts/dejavu-sans.ttf
@@ -56,8 +57,7 @@ func drawWheelSliceLabels(img *image.Paletted, options []string, rotation float6
 		centerX := cx + int(math.Round(math.Cos(angle)*float64(wheelBetaSliceLabelRadius)))
 		centerY := cy + int(math.Round(math.Sin(angle)*float64(wheelBetaSliceLabelRadius)))
 		text := wheelBetaDisplayText(option, limit)
-		drawRotatedCenteredTextAt(img, text, centerX+1, centerY+1, angle, wheelBetaPaperColorIndex)
-		drawRotatedCenteredTextAt(img, text, centerX, centerY, angle, wheelBetaInkColorIndex)
+		drawRotatedCenteredTextAt(img, text, centerX, centerY, angle, wheelBetaInkColorIndex, wheelBetaSliceLabelAlphaThreshold)
 	}
 }
 
@@ -247,7 +247,7 @@ func drawCenteredTextAt(img *image.Paletted, text string, centerX, baselineY int
 	drawer.DrawString(text)
 }
 
-func drawRotatedCenteredTextAt(img *image.Paletted, text string, centerX, centerY int, angle float64, colorIndex byte) {
+func drawRotatedCenteredTextAt(img *image.Paletted, text string, centerX, centerY int, angle float64, colorIndex byte, alphaThreshold byte) {
 	face := newWheelBetaTextFace()
 	defer func() {
 		_ = face.Close()
@@ -265,12 +265,16 @@ func drawRotatedCenteredTextAt(img *image.Paletted, text string, centerX, center
 	}
 	drawer.DrawString(text)
 
+	stampRotatedTextMask(img, mask, centerX, centerY, angle, colorIndex, alphaThreshold)
+}
+
+func stampRotatedTextMask(img *image.Paletted, mask *image.Alpha, centerX, centerY int, angle float64, colorIndex byte, alphaThreshold byte) {
 	sourceCenterX := float64(mask.Bounds().Dx()-1) / 2
 	sourceCenterY := float64(mask.Bounds().Dy()-1) / 2
 	sin, cos := math.Sin(angle), math.Cos(angle)
 	for y := mask.Bounds().Min.Y; y < mask.Bounds().Max.Y; y++ {
 		for x := mask.Bounds().Min.X; x < mask.Bounds().Max.X; x++ {
-			if mask.AlphaAt(x, y).A == 0 {
+			if mask.AlphaAt(x, y).A < alphaThreshold {
 				continue
 			}
 			localX := float64(x) - sourceCenterX