92 lines
2.2 KiB
Go
92 lines
2.2 KiB
Go
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package canvas
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import (
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"bytes"
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"encoding/base64"
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"errors"
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"image"
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"image/png"
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"syscall/js"
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"git.kirsle.net/apps/doodle/lib/render"
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)
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// Texture can hold on to cached image textures.
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type Texture struct {
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data string // data:image/png URI
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image js.Value // DOM image element
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canvas js.Value // Warmed up canvas element
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ctx2d js.Value // 2D drawing context for the canvas.
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width int
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height int
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}
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// StoreTexture caches a texture from a bitmap.
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func (e *Engine) StoreTexture(name string, img image.Image) (render.Texturer, error) {
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var (
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fh = bytes.NewBuffer([]byte{})
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imageSize = img.Bounds().Size()
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width = imageSize.X
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height = imageSize.Y
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)
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// Encode to PNG format.
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if err := png.Encode(fh, img); err != nil {
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return nil, err
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}
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var dataURI = "data:image/png;base64," + base64.StdEncoding.EncodeToString(fh.Bytes())
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tex := &Texture{
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data: dataURI,
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width: width,
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height: height,
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}
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// Preheat a cached Canvas object.
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canvas := js.Global().Get("document").Call("createElement", "canvas")
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canvas.Set("width", width)
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canvas.Set("height", height)
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tex.canvas = canvas
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ctx2d := canvas.Call("getContext", "2d")
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tex.ctx2d = ctx2d
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// Load as a JS Image object.
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image := js.Global().Call("eval", "new Image()")
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image.Call("addEventListener", "load", js.FuncOf(func(this js.Value, args []js.Value) interface{} {
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ctx2d.Call("drawImage", image, 0, 0)
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return nil
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}))
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image.Set("src", tex.data)
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tex.image = image
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// Cache the texture in memory.
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e.textures[name] = tex
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return tex, nil
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}
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// Size returns the dimensions of the texture.
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func (t *Texture) Size() render.Rect {
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return render.NewRect(int32(t.width), int32(t.height))
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}
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// LoadTexture recalls a cached texture image.
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func (e *Engine) LoadTexture(name string) (render.Texturer, error) {
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if tex, ok := e.textures[name]; ok {
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return tex, nil
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}
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return nil, errors.New("no bitmap data stored for " + name)
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}
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// Copy a texturer bitmap onto the canvas.
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func (e *Engine) Copy(t render.Texturer, src, dist render.Rect) {
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tex := t.(*Texture)
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// e.canvas.ctx2d.Call("drawImage", tex.image, dist.X, dist.Y)
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e.canvas.ctx2d.Call("drawImage", tex.canvas, dist.X, dist.Y)
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}
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