80 lines
1.6 KiB
Go
80 lines
1.6 KiB
Go
package engine
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import (
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"compress/gzip"
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"encoding/gob"
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"image"
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"io/fs"
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"github.com/hajimehoshi/ebiten/v2"
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)
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var (
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imageCache = make(map[assetKey]*ebiten.Image)
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// Ensure types satisfy interfaces.
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_ Loader = &ImageRef{}
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)
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func init() {
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gob.Register(ImageRef{})
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}
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type assetKey struct {
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assets fs.FS
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path string
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}
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func loadGobz(dst interface{}, assets fs.FS, path string) error {
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f, err := assets.Open(path)
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if err != nil {
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return err
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}
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defer f.Close()
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gz, err := gzip.NewReader(f)
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if err != nil {
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return err
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}
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return gob.NewDecoder(gz).Decode(dst)
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}
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// ImageRef loads images from the AssetFS into *ebiten.Image form.
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// It is your responsibility to import _ "image/..." for whatever
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// format the files are in, and to load it (either return it as a
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// subcomponent from Scan so that Game will Load it, or call Load
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// yourself).
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type ImageRef struct {
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Path string
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image *ebiten.Image
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}
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// Image returns the image, or nil if not loaded.
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// Multiple distinct ImageRefs can use the same path.
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func (r *ImageRef) Image() *ebiten.Image {
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return r.image
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}
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// Load loads the image. Load is required before Image returns.
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// Loading the same path multiple times uses a cache to return
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// the same image.
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func (r *ImageRef) Load(assets fs.FS) error {
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// Fast path load from cache
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r.image = imageCache[assetKey{assets, r.Path}]
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if r.image != nil {
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return nil
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}
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// Slow path
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f, err := assets.Open(r.Path)
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if err != nil {
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return err
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}
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defer f.Close()
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i, _, err := image.Decode(f)
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if err != nil {
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return err
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}
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r.image = ebiten.NewImageFromImage(i)
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imageCache[assetKey{assets, r.Path}] = r.image
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return nil
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}
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