Use dep to vendor things

vendor/github.com/faiface/pixel/sprite.go

@@ -0,0 +1,117 @@
+package pixel
+
+import "image/color"
+
+// Sprite is a drawable frame of a Picture. It's anchored by the center of it's Picture's frame.
+//
+// Frame specifies a rectangular portion of the Picture that will be drawn. For example, this
+// creates a Sprite that draws the whole Picture:
+//
+//   sprite := pixel.NewSprite(pic, pic.Bounds())
+//
+// Note, that Sprite caches the results of MakePicture from Targets it's drawn to for each Picture
+// it's set to. What it means is that using a Sprite with an unbounded number of Pictures leads to a
+// memory leak, since Sprite caches them and never forgets. In such a situation, create a new Sprite
+// for each Picture.
+type Sprite struct {
+	tri   *TrianglesData
+	frame Rect
+	d     Drawer
+
+	matrix Matrix
+	mask   RGBA
+}
+
+// NewSprite creates a Sprite from the supplied frame of a Picture.
+func NewSprite(pic Picture, frame Rect) *Sprite {
+	tri := MakeTrianglesData(6)
+	s := &Sprite{
+		tri: tri,
+		d:   Drawer{Triangles: tri},
+	}
+	s.matrix = IM
+	s.mask = Alpha(1)
+	s.Set(pic, frame)
+	return s
+}
+
+// Set sets a new frame of a Picture for this Sprite.
+func (s *Sprite) Set(pic Picture, frame Rect) {
+	s.d.Picture = pic
+	if frame != s.frame {
+		s.frame = frame
+		s.calcData()
+	}
+}
+
+// Picture returns the current Sprite's Picture.
+func (s *Sprite) Picture() Picture {
+	return s.d.Picture
+}
+
+// Frame returns the current Sprite's frame.
+func (s *Sprite) Frame() Rect {
+	return s.frame
+}
+
+// Draw draws the Sprite onto the provided Target. The Sprite will be transformed by the given Matrix.
+//
+// This method is equivalent to calling DrawColorMask with nil color mask.
+func (s *Sprite) Draw(t Target, matrix Matrix) {
+	s.DrawColorMask(t, matrix, nil)
+}
+
+// DrawColorMask draws the Sprite onto the provided Target. The Sprite will be transformed by the
+// given Matrix and all of it's color will be multiplied by the given mask.
+//
+// If the mask is nil, a fully opaque white mask will be used, which causes no effect.
+func (s *Sprite) DrawColorMask(t Target, matrix Matrix, mask color.Color) {
+	dirty := false
+	if matrix != s.matrix {
+		s.matrix = matrix
+		dirty = true
+	}
+	if mask == nil {
+		mask = Alpha(1)
+	}
+	rgba := ToRGBA(mask)
+	if rgba != s.mask {
+		s.mask = rgba
+		dirty = true
+	}
+
+	if dirty {
+		s.calcData()
+	}
+
+	s.d.Draw(t)
+}
+
+func (s *Sprite) calcData() {
+	var (
+		center     = s.frame.Center()
+		horizontal = V(s.frame.W()/2, 0)
+		vertical   = V(0, s.frame.H()/2)
+	)
+
+	(*s.tri)[0].Position = Vec{}.Sub(horizontal).Sub(vertical)
+	(*s.tri)[1].Position = Vec{}.Add(horizontal).Sub(vertical)
+	(*s.tri)[2].Position = Vec{}.Add(horizontal).Add(vertical)
+	(*s.tri)[3].Position = Vec{}.Sub(horizontal).Sub(vertical)
+	(*s.tri)[4].Position = Vec{}.Add(horizontal).Add(vertical)
+	(*s.tri)[5].Position = Vec{}.Sub(horizontal).Add(vertical)
+
+	for i := range *s.tri {
+		(*s.tri)[i].Color = s.mask
+		(*s.tri)[i].Picture = center.Add((*s.tri)[i].Position)
+		(*s.tri)[i].Intensity = 1
+	}
+
+	// matrix and mask
+	for i := range *s.tri {
+		(*s.tri)[i].Position = s.matrix.Project((*s.tri)[i].Position)
+		(*s.tri)[i].Color = s.mask
+	}
+
+	s.d.Dirty()
+}