package canvas import ( "bytes" "encoding/base64" "errors" "image" "image/png" "syscall/js" "git.kirsle.net/go/render" ) // Texture can hold on to cached image textures. type Texture struct { data string // data:image/png URI img image.Image // underlying Go image data image js.Value // DOM image element canvas js.Value // Warmed up canvas element ctx2d js.Value // 2D drawing context for the canvas. width int height int } // StoreTexture caches a texture from a bitmap. func (e *Engine) StoreTexture(name string, img image.Image) (render.Texturer, error) { var ( fh = bytes.NewBuffer([]byte{}) imageSize = img.Bounds().Size() width = imageSize.X height = imageSize.Y ) // Encode to PNG format. if err := png.Encode(fh, img); err != nil { return nil, err } var dataURI = "data:image/png;base64," + base64.StdEncoding.EncodeToString(fh.Bytes()) tex := &Texture{ data: dataURI, img: img, width: width, height: height, } // Preheat a cached Canvas object. canvas := js.Global().Get("document").Call("createElement", "canvas") canvas.Set("width", width) canvas.Set("height", height) tex.canvas = canvas ctx2d := canvas.Call("getContext", "2d") tex.ctx2d = ctx2d // Load as a JS Image object. image := js.Global().Call("eval", "new Image()") image.Call("addEventListener", "load", js.FuncOf(func(this js.Value, args []js.Value) interface{} { ctx2d.Call("drawImage", image, 0, 0) return nil })) image.Set("src", tex.data) tex.image = image // Cache the texture in memory. e.textures[name] = tex return tex, nil } // Size returns the dimensions of the texture. func (t *Texture) Size() render.Rect { return render.NewRect(t.width, t.height) } // Image returns the underlying image. func (t *Texture) Image() image.Image { return nil } // Free the texture. Doesn't do anything in the Canvas engine currently. func (t *Texture) Free() error { return nil } // LoadTexture recalls a cached texture image. func (e *Engine) LoadTexture(name string) (render.Texturer, error) { if tex, ok := e.textures[name]; ok { return tex, nil } return nil, errors.New("no bitmap data stored for " + name) } // Copy a texturer bitmap onto the canvas. func (e *Engine) Copy(t render.Texturer, src, dist render.Rect) { tex := t.(*Texture) // e.canvas.ctx2d.Call("drawImage", tex.image, dist.X, dist.Y) e.canvas.ctx2d.Call("drawImage", tex.canvas, dist.X, dist.Y) } // FreeTextures flushes the texture cache. func (e *Engine) FreeTextures() int { var len = len(e.textures) for name := range e.textures { delete(e.textures, name) } return len }