modelize titles and backgrounds

src/idz/encoder/_bitmap.ts

@@ -0,0 +1,12 @@
+export function bitmap(items: number[], nbytes: number): Buffer {
+  const buf = Buffer.alloc(nbytes);
+
+  for (const item of items) {
+    const byte = (item / 8) | 0;
+    const bit = item % 8;
+
+    buf.writeUInt8(buf.readUInt8(byte) | (1 << bit), byte);
+  }
+
+  return buf;
+}