fix: limit max blur radius to 254

stackblur.go

@@ -70,6 +70,15 @@ func StackBlur(img *image.NRGBA, radius uint32) *image.NRGBA {
 		pr, pg, pb, pa uint32
 	)
 
+	// Limit the maximum blur radius to 255, otherwise it overflows the multable length
+	// and will panic with and index out of range error.
+	if int(radius) >= len(mulTable) {
+		radius = uint32(len(mulTable) - 1)
+	}
+	if radius < 1 {
+		radius = 1
+	}
+
 	div = radius + radius + 1
 	widthMinus1 = width - 1
 	heightMinus1 = height - 1