diff --git a/image/color/hsv.go b/image/color/hsv.go
index 80334ea..2d2495d 100644
--- a/image/color/hsv.go
+++ b/image/color/hsv.go
@@ -67,12 +67,7 @@ func (hsva HSVA) RGBA () (r, g, b, a uint32) {
 		S: hsva.S,
 		V: hsva.V,
 	}.RGBA()
-	a = uint32(hsva.A)
-	// alpha premultiplication
-	r = (r * a) / 0xFFFF
-	g = (g * a) / 0xFFFF
-	b = (b * a) / 0xFFFF
-	return
+	return Premultiply(r, g, b, uint32(hsva.A))
 }
 
 // Canon returns the color but with the H, S, and V fields are constrained to
@@ -104,11 +99,7 @@ func hsvModel (c color.Color) color.Color {
 	case HSV:  return c
 	case HSVA: return HSV { H: c.H, S: c.S, V: c.V }
 	default:
-		r, g, b, a := c.RGBA()
-		// alpha unpremultiplication
-		r = (r / a) * 0xFFFF
-		g = (g / a) * 0xFFFF
-		b = (b / a) * 0xFFFF
+		r, g, b, _ := Unpremultiply(c.RGBA())
 		return rgbToHSV(r, g, b)
 	}
 }