repackage code to cmd

cmd/camera.go

@@ -0,0 +1,81 @@
+// this comes from the camera example but I enhanced it a little bit
+
+package cmd
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"golang.org/x/image/math/f64"
+)
+
+type Camera struct {
+	ViewPort          f64.Vec2
+	Position          f64.Vec2
+	ZoomFactor        int
+	InitialZoomFactor int
+	InitialPosition   f64.Vec2
+	ZoomOutFactor     int
+}
+
+func (c *Camera) String() string {
+	return fmt.Sprintf(
+		"T: %.1f, S: %d",
+		c.Position, c.ZoomFactor,
+	)
+}
+
+func (c *Camera) viewportCenter() f64.Vec2 {
+	return f64.Vec2{
+		c.ViewPort[0] * 0.5,
+		c.ViewPort[1] * 0.5,
+	}
+}
+
+func (c *Camera) worldMatrix() ebiten.GeoM {
+	m := ebiten.GeoM{}
+	m.Translate(-c.Position[0], -c.Position[1])
+
+	viewportCenter := c.viewportCenter()
+
+	// We want to scale and rotate around center of image / screen
+	m.Translate(-viewportCenter[0], -viewportCenter[1])
+
+	m.Scale(
+		math.Pow(1.01, float64(c.ZoomFactor)),
+		math.Pow(1.01, float64(c.ZoomFactor)),
+	)
+
+	m.Translate(viewportCenter[0], viewportCenter[1])
+	return m
+}
+
+func (c *Camera) Render(world, screen *ebiten.Image) {
+	screen.DrawImage(world, &ebiten.DrawImageOptions{
+		GeoM: c.worldMatrix(),
+	})
+}
+
+func (c *Camera) ScreenToWorld(posX, posY int) (float64, float64) {
+	inverseMatrix := c.worldMatrix()
+	if inverseMatrix.IsInvertible() {
+		inverseMatrix.Invert()
+		return inverseMatrix.Apply(float64(posX), float64(posY))
+	} else {
+		// When scaling it can happened that matrix is not invertable
+		return math.NaN(), math.NaN()
+	}
+}
+
+func (c *Camera) Setup() {
+	c.Position[0] = c.InitialPosition[0]
+	c.Position[1] = c.InitialPosition[1]
+	c.ZoomFactor = c.InitialZoomFactor
+}
+
+func (c *Camera) Reset() {
+	c.Position[0] = c.InitialPosition[0]
+	c.Position[1] = c.InitialPosition[1]
+	c.ZoomFactor = c.ZoomOutFactor
+}