add 16 wide, 2 deep tree with RLE at the end. turns out to be worse than other algs

encoder/src/enc.rs

@@ -293,6 +293,71 @@ pub fn rle_horizontal(_prev_frame: &Frame, frame: &Frame) -> EncodedFrame {
 	}
 }
 
+/// requires WIDTH and HEIGHT to be multiples of 16
+/// two-level tree with 4x4 branches per level
+pub fn tree_16(_prev_frame: &Frame, frame: &Frame) -> EncodedFrame {
+	let mut top_node: u16 = 0;
+	let mut second_nodes = Vec::new();
+	let mut included_pixels = Vec::new();
+	// todo allow using white as bg
+	let fg = 1;
+	for cx in 0..4 {
+		for cy in 0..4 {
+			let mut any_filled_here = false;
+			'a: for px in 0..(WIDTH / 4) {
+				let x = cx * (WIDTH / 4) + px;
+				for py in 0..(HEIGHT / 4) {
+					let y = cy * (HEIGHT / 4) + py;
+					if frame[x][y] == fg{
+						any_filled_here = true;
+						break 'a;
+					}
+				}
+			}
+			if any_filled_here {
+				top_node |= 1 << (cy * 4 + cx);
+				let mut second_node: u16 = 0;
+				for ccx in 0..4 {
+					for ccy in 0..4 {
+						let mut any_filled_here = false;
+						let mut node_pixels = Vec::new();
+						for px in 0..(WIDTH / 16) {
+							for py in 0..(HEIGHT / 16) {
+								let x = cx * (WIDTH / 4) + ccx * (WIDTH / 16) + px;
+								let y = cy * (HEIGHT / 4) + ccy * (HEIGHT / 16) + py;
+								if frame[x][y] == fg {
+									node_pixels.push(fg);
+									any_filled_here = true;
+								}else{
+									node_pixels.push(1-fg);
+								}
+							}
+						}
+						if any_filled_here {
+							second_node |= 1 << (ccy * 4 + ccx);
+							included_pixels.extend_from_slice(&node_pixels);
+						}
+					}
+				}
+				second_nodes.push(second_node);
+			}
+		}
+	}
+	let mut data = Vec::new();
+	data.push((top_node >>8) as u8);
+	data.push(top_node as u8);
+	for n in second_nodes{
+		data.push((n>>8)as u8);
+		data.push(n as u8);
+	}
+	data.extend_from_slice(&rle_255_encode(&included_pixels));
+
+	EncodedFrame {
+		encoding: Encoding::Tree16,
+		data,
+	}
+}
+
 pub fn rle_vertical(_prev_frame: &Frame, frame: &Frame) -> EncodedFrame {
 	let mut pixels = Vec::new();
 	for x in 0..WIDTH {
@@ -348,7 +413,6 @@ pub fn rle_vertical_ext(_prev_frame: &Frame, frame: &Frame) -> EncodedFrame {
 	}
 }
 
-
 pub fn rle_vertical_16(_prev_frame: &Frame, frame: &Frame) -> EncodedFrame {
 	let mut data = Vec::new();
 	let mut last_pixel = 0;