[WIP] start 1.15 port

reorganize packages to match Fabric version
use util classes from Fabric version

src/main/kotlin/mods/betterfoliage/resource/generated/CenteringTextureGenerator.kt

@@ -0,0 +1,39 @@
+package mods.betterfoliage.resource.generated
+
+import mods.betterfoliage.resource.Identifier
+import mods.betterfoliage.texture.loadSprite
+import mods.betterfoliage.util.Atlas
+import mods.betterfoliage.util.bytes
+import net.minecraft.resources.IResourceManager
+import java.awt.image.BufferedImage
+import java.lang.Math.max
+
+data class CenteredSprite(val sprite: Identifier, val atlas: Atlas = Atlas.BLOCKS, val aspectHeight: Int = 1, val aspectWidth: Int = 1) {
+
+    fun register(pack: GeneratedBlockTexturePack) = pack.register(this, this::draw)
+
+    fun draw(resourceManager: IResourceManager): ByteArray {
+        val baseTexture = resourceManager.loadSprite(atlas.wrap(sprite))
+
+        val frameWidth = baseTexture.width
+        val frameHeight = baseTexture.width * aspectHeight / aspectWidth
+        val frames = baseTexture.height / frameHeight
+        val size = max(frameWidth, frameHeight)
+
+        val resultTexture = BufferedImage(size, size * frames, BufferedImage.TYPE_4BYTE_ABGR)
+        val graphics = resultTexture.createGraphics()
+
+        // iterate all frames
+        for (frame in 0 until frames) {
+            val baseFrame = baseTexture.getSubimage(0, size * frame, frameWidth, frameHeight)
+            val resultFrame = BufferedImage(size, size, BufferedImage.TYPE_4BYTE_ABGR)
+
+            resultFrame.createGraphics().apply {
+                drawImage(baseFrame, (size - frameWidth) / 2, (size - frameHeight) / 2, null)
+            }
+            graphics.drawImage(resultFrame, 0, size * frame, null)
+        }
+
+        return resultTexture.bytes
+    }
+}