A rendering engine library for Go supporting both SDL2 and WebAssembly (HTML Canvas) targets.
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package sdl
import (
// Copy a texture into the renderer.
func (r *Renderer) Copy(t render.Texturer, src, dst render.Rect) {
if tex, ok := t.(*Texture); ok {
var (
a = RectToSDL(src)
b = RectToSDL(dst)
r.renderer.Copy(tex.tex, &a, &b)
// Texture can hold on to SDL textures for caching and optimization.
type Texture struct {
tex *sdl.Texture
width int32
height int32
// NewTexture caches an SDL texture from a bitmap.
func (r *Renderer) NewTexture(filename string, img image.Image) (render.Texturer, error) {
fh, err := os.Create(filename)
if err != nil {
return nil, err
defer fh.Close()
err = bmp.Encode(fh, img)
return nil, err
// Size returns the dimensions of the texture.
func (t *Texture) Size() render.Rect {
return render.NewRect(t.width, t.height)
// NewBitmap initializes a texture from a bitmap image.
func (r *Renderer) NewBitmap(filename string) (render.Texturer, error) {
surface, err := sdl.LoadBMP(filename)
if err != nil {
return nil, fmt.Errorf("NewBitmap: LoadBMP: %s", err)
defer surface.Free()
// TODO: chroma key color hardcoded to white here
key := sdl.MapRGB(surface.Format, 255, 255, 255)
surface.SetColorKey(true, key)
tex, err := r.renderer.CreateTextureFromSurface(surface)
if err != nil {
return nil, fmt.Errorf("NewBitmap: create texture: %s", err)
return &Texture{
width: surface.W,
height: surface.H,
tex: tex,
}, nil