fix: set color min/max range

internal/color/color.go

@@ -2,6 +2,7 @@ package color
 
 import (
 	"image"
+	"math"
 
 	"github.com/lucasb-eyer/go-colorful"
 )
@@ -41,9 +42,13 @@ func GetRgbAverage(i *image.RGBA) RGB {
 		}
 	}
 
+	rangeValue := func(v float64) float64 {
+		return math.Min(250, math.Max(10, v))
+	}
+
 	return RGB{
-		R: float64(rSum) / float64(count),
-		G: float64(gSum) / float64(count),
-		B: float64(bSum) / float64(count),
+		R: rangeValue(float64(rSum) / float64(count)),
+		G: rangeValue(float64(gSum) / float64(count)),
+		B: rangeValue(float64(bSum) / float64(count)),
 	}
 }