reorganized source, added test cases for tuning

src/loader-sprites.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"embed"
+	"image"
+	_ "image/png"
+	"io/fs"
+	"log"
+	"path"
+	"strings"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+// Maps image name to image data
+type AssetRegistry map[string]*ebiten.Image
+
+// A helper to pass the registry easier around
+type assetData struct {
+	Registry AssetRegistry
+}
+
+//go:embed assets/sprites/*.png assets/fonts/*.ttf assets/shaders/*.kg
+var assetfs embed.FS
+
+// Called at build time, creates the global asset and animation registries
+var Assets = LoadImages("assets/sprites")
+
+// load pngs and json files
+func LoadImages(dir string) AssetRegistry {
+	Registry := AssetRegistry{}
+
+	// we use embed.FS to iterate over all files in ./assets/
+	entries, err := assetfs.ReadDir(dir)
+	if err != nil {
+		log.Fatalf("failed to read assets dir %s: %s", dir, err)
+	}
+
+	for _, imagefile := range entries {
+		path := path.Join(dir, imagefile.Name())
+
+		fd, err := assetfs.Open(path)
+		if err != nil {
+			log.Fatalf("failed to open file %s: %s", imagefile.Name(), err)
+		}
+		defer fd.Close()
+
+		switch {
+		case strings.HasSuffix(path, ".png"):
+			name, image := ReadImage(imagefile, fd)
+			Registry[name] = image
+		}
+	}
+
+	return Registry
+}
+
+func ReadImage(imagefile fs.DirEntry, fd fs.File) (string, *ebiten.Image) {
+	name := strings.TrimSuffix(imagefile.Name(), ".png")
+
+	img, _, err := image.Decode(fd)
+	if err != nil {
+		log.Fatalf("failed to decode image %s: %s", imagefile.Name(), err)
+	}
+
+	image := ebiten.NewImageFromImage(img)
+
+	return name, image
+}