ebitengine-graphics

Overview

A package implementing various graphics primitives like Sprite for Ebitengine.

It works the best in combination with gscene package, but can be used without it.

Graphical objects list:

• Sprite
• Line
• Rect
• Container

Missing some graphical object? Tell us about it.

Installation

go get github.com/quasilyte/ebitengine-graphics

Quick Start

The most useful type of this package is Sprite, but it's tricky to demonstrate its usage without assets. This is a quick start section, it's intended to be as slim as possible.

You can use this library without gscene:

package main

import (
	"github.com/hajimehoshi/ebiten/v2"
	graphics "github.com/quasilyte/ebitengine-graphics"
	"github.com/quasilyte/gmath"
)

func main() {
	ebiten.SetWindowSize(640, 480)
	if err := ebiten.RunGame(newExampleGame()); err != nil {
		panic(err)
	}
}

type exampleGame struct {
	pos           gmath.Vec
	initialized   bool
	objects       []drawable
}

type drawable interface {
	Draw(screen *ebiten.Image)
}

func newExampleGame() *exampleGame {
	return &exampleGame{
		pos:           gmath.Vec{X: 32, Y: 32},
	}
}

func (g *exampleGame) Layout(outsideWidth, outsideHeight int) (int, int) {
	return 640, 480
}

func (g *exampleGame) Draw(screen *ebiten.Image) {
	for _, o := range g.objects {
		o.Draw(screen)
	}
}

func (g *exampleGame) Update() error {
	if !g.initialized {
		g.Init()
		g.initialized = true
	}

	g.pos = g.pos.Add(gmath.Vec{X: 1, Y: 2})
	return nil
}

func (g *exampleGame) Init() {
	{
		from := gmath.Pos{Base: &g.pos}
		to := gmath.Pos{Offset: gmath.Vec{X: 128, Y: 64}}
		l := graphics.NewLine(from, to)
		l.SetWidth(2)
		l.SetColorScale(graphics.ColorScaleFromRGBA(200, 100, 100, 255))
		g.objects = append(g.objects, l)
	}

	{
		r := graphics.NewRect(32, 32)
		r.Pos.Base = &g.pos
		r.SetFillColorScale(graphics.RGB(0xAABB00))
		r.SetOutlineColorScale(graphics.RGB(0x0055ff))
		r.SetOutlineWidth(2)
		g.objects = append(g.objects, r)
	}
}

With gscene it's even easier (showing only relevant part):

func (c *exampleController) Init(scene *gscene.SimpleRootScene) {
	{
		from := gmath.Pos{Base: &g.pos}
		to := gmath.Pos{Offset: gmath.Vec{X: 128, Y: 64}}
		l := graphics.NewLine(from, to)
		l.SetWidth(2)
		l.SetColorScale(graphics.ColorScaleFromRGBA(200, 100, 100, 255))
		scene.AddGraphics(l)
	}

	{
		r := graphics.NewRect(32, 32)
		r.Pos.Base = &g.pos
		r.SetFillColorScale(graphics.RGB(0xAABB00))
		r.SetOutlineColorScale(graphics.RGB(0x0055ff))
		r.SetOutlineWidth(2)
		scene.AddGraphics(r)
	}
}

Note that we can add the graphical object directly to the scene. The scene will manage their Draw calls as well as their lifetimes (based on graphical objects being disposed or not).