add Sprite.SetMatrix and Sprite.SetColorMask

sprite.go

@@ -1,10 +1,16 @@
 package pixel
 
-// Sprite is a drawable Picture. It's always anchored by the center of it's Picture.
+// Sprite is a drawable Picture. It's anchored by the center of it's Picture.
+//
+// To achieve different anchoring, transformations and color masking, use SetMatrix and SetColorMask
+// methods.
 type Sprite struct {
 	tri    *TrianglesData
 	bounds Rect
 	d      Drawer
+
+	matrix Matrix
+	mask   NRGBA
 }
 
 // NewSprite creates a Sprite from the supplied Picture.
@@ -14,6 +20,8 @@ func NewSprite(pic Picture) *Sprite {
 		tri: tri,
 		d:   Drawer{Triangles: tri},
 	}
+	s.matrix = IM
+	s.mask = NRGBA{1, 1, 1, 1}
 	s.SetPicture(pic)
 	return s
 }
@@ -28,6 +36,40 @@ func (s *Sprite) SetPicture(pic Picture) {
 	}
 	s.bounds = pic.Bounds()
 
+	s.calcData()
+}
+
+// Picture returns the current Sprite's Picture.
+func (s *Sprite) Picture() Picture {
+	return s.d.Picture
+}
+
+// SetMatrix sets a Matrix that this Sprite will be transformed by. This overrides any previously
+// set Matrix.
+//
+// Note, that this has nothing to do with BasicTarget's SetMatrix method. This only affects this
+// Sprite and is usable with any Target.
+func (s *Sprite) SetMatrix(matrix Matrix) {
+	s.matrix = matrix
+	s.calcData()
+}
+
+// SetColorMask sets a color that this Sprite will be multiplied by. This overrides any previously
+// set color mask.
+//
+// Note, that this has nothing to do with BasicTarget's SetColorMask method. This only affects this
+// Sprite and is usable with any Target.
+func (s *Sprite) SetColorMask(mask NRGBA) {
+	s.mask = mask
+	s.calcData()
+}
+
+// Draw draws the Sprite onto the provided Target.
+func (s *Sprite) Draw(t Target) {
+	s.d.Draw(t)
+}
+
+func (s *Sprite) calcData() {
 	var (
 		center     = s.bounds.Center()
 		horizontal = X(s.bounds.W() / 2)
@@ -42,20 +84,12 @@ func (s *Sprite) SetPicture(pic Picture) {
 	(*s.tri)[5].Position = -horizontal + vertical
 
 	for i := range *s.tri {
-		(*s.tri)[i].Color = NRGBA{1, 1, 1, 1}
+		(*s.tri)[i].Color = s.mask
 		(*s.tri)[i].Picture = center + (*s.tri)[i].Position
 		(*s.tri)[i].Intensity = 1
+
+		(*s.tri)[i].Position = s.matrix.Project((*s.tri)[i].Position)
 	}
 
 	s.d.Dirty()
 }
-
-// Picture returns the current Sprite's Picture.
-func (s *Sprite) Picture() Picture {
-	return s.d.Picture
-}
-
-// Draw draws the Sprite onto the provided Target.
-func (s *Sprite) Draw(t Target) {
-	s.d.Draw(t)
-}