Minor change for legibility

Slight change to the AdjustHue function to adjust readability.

adjust.go

@@ -95,11 +95,12 @@ func AdjustHue(img image.Image, shift float64) *image.NRGBA {
 	}
 
 	shift = math.Min(math.Max(shift, -180), 180)
-	shift = shift / -360
+	summand := shift / -360
 
 	return AdjustFunc(img, func(c color.NRGBA) color.NRGBA {
 		h, s, l := rgbToHSL(c.R, c.G, c.B)
-		h = math.Mod(h+shift, 1.0)
+		h += summand
+		h = math.Mod(h, 1.0)
 		r, g, b := hslToRGB(h, s, l)
 		return color.NRGBA{r, g, b, c.A}
 	})