fix wrong git ignore

internal/pdf/contentstream/draw/vector.go

@@ -0,0 +1,80 @@
+package draw
+
+import "math"
+
+type Vector struct {
+	Dx float64
+	Dy float64
+}
+
+func NewVector(dx, dy float64) Vector {
+	v := Vector{}
+	v.Dx = dx
+	v.Dy = dy
+	return v
+}
+
+func NewVectorBetween(a Point, b Point) Vector {
+	v := Vector{}
+	v.Dx = b.X - a.X
+	v.Dy = b.Y - a.Y
+	return v
+}
+
+func NewVectorPolar(length float64, theta float64) Vector {
+	v := Vector{}
+
+	v.Dx = length * math.Cos(theta)
+	v.Dy = length * math.Sin(theta)
+	return v
+}
+
+func (v Vector) Add(other Vector) Vector {
+	v.Dx += other.Dx
+	v.Dy += other.Dy
+	return v
+}
+
+func (v Vector) Rotate(phi float64) Vector {
+	mag := v.Magnitude()
+	angle := v.GetPolarAngle()
+
+	return NewVectorPolar(mag, angle+phi)
+}
+
+// Change the sign of the vector: -vector.
+func (this Vector) Flip() Vector {
+	mag := this.Magnitude()
+	theta := this.GetPolarAngle()
+
+	this.Dx = mag * math.Cos(theta+math.Pi)
+	this.Dy = mag * math.Sin(theta+math.Pi)
+	return this
+}
+
+func (v Vector) FlipY() Vector {
+	v.Dy = -v.Dy
+	return v
+}
+
+func (v Vector) FlipX() Vector {
+	v.Dx = -v.Dx
+	return v
+}
+
+func (this Vector) Scale(factor float64) Vector {
+	mag := this.Magnitude()
+	theta := this.GetPolarAngle()
+
+	this.Dx = factor * mag * math.Cos(theta)
+	this.Dy = factor * mag * math.Sin(theta)
+	return this
+}
+
+func (this Vector) Magnitude() float64 {
+	return math.Sqrt(math.Pow(this.Dx, 2.0) + math.Pow(this.Dy, 2.0))
+}
+
+func (this Vector) GetPolarAngle() float64 {
+	return math.Atan2(this.Dy, this.Dx)
+}