Add exp/shape package

example/shapes/main.go

@@ -16,8 +16,10 @@ package main
 
 import (
 	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/exp/shape"
 	"image/color"
 	"log"
+	"math"
 )
 
 const (
@@ -33,6 +35,9 @@ func update(screen *ebiten.Image) error {
 	screen.FillRect(20, 20, 100, 100, color.NRGBA{0x80, 0x80, 0xff, 0x80})
 	screen.DrawLine(130, 0, 140, 100, color.NRGBA{0xff, 0x80, 0x80, 0x80})
 	screen.DrawLine(140, 0, 150, 100, color.NRGBA{0xff, 0x80, 0x80, 0x80})
+
+	shape.DrawEllipse(screen, 0, 0, 100, 50, color.NRGBA{0x80, 0xff, 0x80, 0x80})
+	shape.DrawArc(screen, 0, 0, 100, 50, 0, math.Pi/2, color.NRGBA{0xff, 0x80, 0x80, 0x80})
 	return nil
 }
 

exp/shape/ellipse.go

@@ -0,0 +1,90 @@
+// Copyright 2015 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package shape
+
+import (
+	"github.com/hajimehoshi/ebiten"
+	"image/color"
+	"math"
+)
+
+func DrawEllipse(s *ebiten.Image, x, y, width, height int, clr color.Color) error {
+	return s.DrawLines(&ellipsesLines{&rect{x, y, width, height, clr}, 0, 2 * math.Pi})
+}
+
+func DrawEllipses(s *ebiten.Image, rects ebiten.Rects) error {
+	return s.DrawLines(&ellipsesLines{rects, 0, 2 * math.Pi})
+}
+
+func DrawArc(s *ebiten.Image, x, y, width, height int, angle0, angle1 float64, clr color.Color) error {
+	return s.DrawLines(&ellipsesLines{&rect{x, y, width, height, clr}, angle0, angle1})
+}
+
+type ellipsesLines struct {
+	ebiten.Rects
+	angle0, angle1 float64
+}
+
+func (e *ellipsesLines) lineNum() int {
+	return 64
+}
+
+func (e *ellipsesLines) Len() int {
+	return e.Rects.Len() * e.lineNum()
+}
+
+func (e *ellipsesLines) Points(i int) (x0, y0, x1, y1 int) {
+	n := e.lineNum()
+	x, y, w, h := e.Rects.Rect(i / n)
+	part := float64(i % n)
+	theta0 := 2 * math.Pi * part / float64(n)
+	theta1 := 2 * math.Pi * (part + 1) / float64(n)
+	if theta0 < e.angle0 || e.angle1 < theta1 {
+		return 0, 0, 0, 0
+	}
+	theta0 = math.Max(theta0, e.angle0)
+	theta1 = math.Min(theta1, e.angle1)
+	fy0, fx0 := math.Sincos(theta0)
+	fy1, fx1 := math.Sincos(theta1)
+	hw, hh := (float64(w)-1)/2, (float64(h)-1)/2
+	fx0 = fx0*hw + float64(x) + hw
+	fx1 = fx1*hw + float64(x) + hw
+	fy0 = fy0*hh + float64(y) + hh
+	fy1 = fy1*hh + float64(y) + hh
+	return int(fx0), int(fy0), int(fx1), int(fy1)
+}
+
+func (e *ellipsesLines) Color(i int) color.Color {
+	return e.Rects.Color(i / e.lineNum())
+}
+
+// TODO: This is same as ebiten.rect.
+type rect struct {
+	x, y          int
+	width, height int
+	color         color.Color
+}
+
+func (r *rect) Len() int {
+	return 1
+}
+
+func (r *rect) Rect(i int) (x, y, width, height int) {
+	return r.x, r.y, r.width, r.height
+}
+
+func (r *rect) Color(i int) color.Color {
+	return r.color
+}