ebitenutil: Add DrawLine and DrawRect

Add new APIs DrawLine and DrawRect mainly for debugging or prototyping purpose. Also add examples/shapes.

ebitenutil/shapes.go

@@ -0,0 +1,70 @@
+// Copyright 2017 The Ebiten Authors
+//
+// 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 ebitenutil
+
+import (
+	"image/color"
+	"math"
+
+	"github.com/hajimehoshi/ebiten"
+)
+
+var emptyImage *ebiten.Image
+
+func init() {
+	emptyImage, _ = ebiten.NewImage(16, 16, ebiten.FilterLinear)
+	_ = emptyImage.Fill(color.White)
+}
+
+func colorScale(clr color.Color) (rf, gf, bf, af float64) {
+	r, g, b, a := clr.RGBA()
+	if a == 0 {
+		return 0, 0, 0, 0
+	}
+
+	rf = float64(r) / float64(a)
+	gf = float64(g) / float64(a)
+	bf = float64(b) / float64(a)
+	af = float64(a) / 0xffff
+	return
+}
+
+// DrawLine draws a line on the given destination dst.
+//
+// DrawLine is intented to be used mainly for debugging or prototyping purpose.
+func DrawLine(dst *ebiten.Image, x1, y1, x2, y2 float64, clr color.Color) {
+	ew, eh := emptyImage.Size()
+	length := math.Hypot(x2-x1, y2-y1)
+
+	op := &ebiten.DrawImageOptions{}
+	op.GeoM.Scale(length/float64(ew), 1/float64(eh))
+	op.GeoM.Rotate(math.Atan2(y2-y1, x2-x1))
+	op.GeoM.Translate(x1, y1)
+	op.ColorM.Scale(colorScale(clr))
+	_ = dst.DrawImage(emptyImage, op)
+}
+
+// DrawRect draws a rectangle on the given destination dst.
+//
+// DrawRect is intented to be used mainly for debugging or prototyping purpose.
+func DrawRect(dst *ebiten.Image, x, y, width, height float64, clr color.Color) {
+	ew, eh := emptyImage.Size()
+
+	op := &ebiten.DrawImageOptions{}
+	op.GeoM.Scale(width/float64(ew), height/float64(eh))
+	op.GeoM.Translate(x, y)
+	op.ColorM.Scale(colorScale(clr))
+	_ = dst.DrawImage(emptyImage, op)
+}

examples/shapes/main.go

@@ -0,0 +1,58 @@
+// Copyright 2017 The Ebiten Authors
+//
+// 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.
+
+// +build example
+
+package main
+
+import (
+	"fmt"
+	"image/color"
+	"log"
+
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+)
+
+const (
+	screenWidth  = 640
+	screenHeight = 480
+)
+
+var count = 0
+
+func update(screen *ebiten.Image) error {
+	count++
+	count %= 240
+
+	if ebiten.IsRunningSlowly() {
+		return nil
+	}
+
+	cf := float64(count)
+	ebitenutil.DrawLine(screen, 100, 100, 300, 100, color.RGBA{0xff, 0, 0xff, 0xff})
+	ebitenutil.DrawLine(screen, 50, 150, 50, 350, color.RGBA{0xff, 0xff, 0, 0xff})
+	ebitenutil.DrawLine(screen, 50, 100+cf, 200+cf, 250, color.RGBA{0x00, 0xff, 0xff, 0xff})
+	ebitenutil.DrawRect(screen, 50+cf, 50+cf, 100+cf, 100+cf, color.RGBA{0x80, 0x80, 0x80, 0x80})
+	ebitenutil.DrawRect(screen, 300-cf, 50, 120, 120, color.RGBA{0x00, 0x80, 0x00, 0x80})
+
+	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f", ebiten.CurrentFPS()))
+	return nil
+}
+
+func main() {
+	if err := ebiten.Run(update, screenWidth, screenHeight, 1, "Shapes (Ebiten Demo)"); err != nil {
+		log.Fatal(err)
+	}
+}