Softer attenuation on the NTSC filter

screen/ntscFilter.go

@@ -38,7 +38,7 @@ func buildAttenuatedColorMap(colorMap [16]color.Color) [16]color.Color {
 	for i := 0; i < len(colorMap); i++ {
 		r, g, b, _ := colorMap[i].RGBA()
 		colors[i] = color.RGBA64{
-			uint16(r / 2), uint16(g / 2), uint16(b / 2),
+			uint16(4 * r / 5), uint16(4 * g / 5), uint16(4 * b / 5),
 			65535,
 		}
 	}