glyph texture atlas

src/net/torvald/terrarumsansbitmap/gdx/GlyphAtlas.kt

@@ -0,0 +1,81 @@
+package net.torvald.terrarumsansbitmap.gdx
+
+import com.badlogic.gdx.graphics.Pixmap
+
+data class AtlasRegion(
+    val atlasX: Int,
+    val atlasY: Int,
+    val width: Int,
+    val height: Int,
+    val offsetX: Int = 0,
+    val offsetY: Int = 0
+)
+
+class GlyphAtlas(val atlasWidth: Int, val atlasHeight: Int) {
+
+    val pixmap = Pixmap(atlasWidth, atlasHeight, Pixmap.Format.RGBA8888).also { it.blending = Pixmap.Blending.None }
+
+    private val regions = HashMap<Long, AtlasRegion>()
+
+    private var cursorX = 0
+    private var cursorY = 0
+    private var shelfHeight = 0
+
+    private fun atlasKey(sheetID: Int, cellX: Int, cellY: Int): Long =
+        sheetID.toLong().shl(32) or cellX.toLong().shl(16) or cellY.toLong()
+
+    fun packCell(sheetID: Int, cellX: Int, cellY: Int, cellPixmap: Pixmap) {
+        val w = cellPixmap.width
+        val h = cellPixmap.height
+
+        if (cursorX + w > atlasWidth) {
+            cursorX = 0
+            cursorY += shelfHeight
+            shelfHeight = 0
+        }
+
+        pixmap.drawPixmap(cellPixmap, cursorX, cursorY)
+
+        regions[atlasKey(sheetID, cellX, cellY)] = AtlasRegion(cursorX, cursorY, w, h)
+
+        cursorX += w
+        if (h > shelfHeight) shelfHeight = h
+    }
+
+    fun blitSheet(sheetID: Int, sheetPixmap: Pixmap, cellW: Int, cellH: Int, cols: Int, rows: Int) {
+        if (cursorX > 0) {
+            cursorX = 0
+            cursorY += shelfHeight
+            shelfHeight = 0
+        }
+
+        val baseY = cursorY
+
+        pixmap.drawPixmap(sheetPixmap, 0, baseY)
+
+        for (cy in 0 until rows) {
+            for (cx in 0 until cols) {
+                regions[atlasKey(sheetID, cx, cy)] = AtlasRegion(cx * cellW, baseY + cy * cellH, cellW, cellH)
+            }
+        }
+
+        cursorY = baseY + sheetPixmap.height
+        cursorX = 0
+        shelfHeight = 0
+    }
+
+    fun getRegion(sheetID: Int, cellX: Int, cellY: Int): AtlasRegion? =
+        regions[atlasKey(sheetID, cellX, cellY)]
+
+    fun clearRegion(region: AtlasRegion) {
+        for (y in 0 until region.height) {
+            for (x in 0 until region.width) {
+                pixmap.drawPixel(region.atlasX + x, region.atlasY + y, 0)
+            }
+        }
+    }
+
+    fun dispose() {
+        pixmap.dispose()
+    }
+}