graphics: add line

1 files changed, 76 insertions, 0 deletions

diff --git a/src/estd/graphics/line.zig b/src/estd/graphics/line.zig
new file mode 100644
index 0000000..93f17ff
--- /dev/null
+++ b/src/estd/graphics/line.zig
@@ -0,0 +1,76 @@
+const std = @import("std");
+const graphics = @import("root.zig");
+
+pub const Line = struct {
+	const Self = @This();
+	const Point = struct {
+		x: u32,
+		y: u32,
+	};
+
+	start: Point,
+	end: Point,
+
+	color: graphics.Color,
+
+	fn distance(a: u32, b: u32) u32 {
+		if (a < b) {
+			return b - a;
+		} else {
+			return a - b;
+		}
+	}
+
+	pub fn render(self: *const Self, canvas: *const graphics.Canvas) void {
+		var start = self.start;
+		var end = self.end;
+		const steep = distance(start.y, end.y) > distance(start.x, end.x);
+
+		if (steep) {
+			std.mem.swap(u32, &start.x, &start.y);
+			std.mem.swap(u32, &end.x, &end.y);
+		}
+
+		if (start.x > end.x) {
+			std.mem.swap(Point, &start, &end);
+		}
+
+		const dx: f64 = @floatFromInt(end.x - start.x);
+		const dy: f64 = @floatFromInt(@as(i64, @intCast(end.y)) - @as(i64, @intCast(start.y)));
+		var gradient: f64 = dy / dx;
+		if  (dx == 0) {
+			gradient = 1;
+		}
+
+
+		var intersect_y: f64 = @floatFromInt(start.y);
+
+		if (steep) {
+			for (start.x..end.x + 1) |x| {
+				const y: usize = @intFromFloat(intersect_y);
+				const factor = intersect_y - @as(f64, @floatFromInt(y));
+
+				var previous_color = canvas.buffer[canvas.width * x + y];
+				canvas.buffer[x * canvas.width + y] = previous_color.mix(&self.color, factor);
+
+				previous_color = canvas.buffer[x * canvas.width + y - 1];
+				canvas.buffer[x * canvas.width + y - 1] = self.color.mix(&previous_color, factor);
+
+				intersect_y += gradient;
+			}
+		} else {
+			for (start.x..end.x + 1) |x| {
+				const y: u32 = @intFromFloat(intersect_y);
+				const factor = intersect_y - @as(f64, @floatFromInt(y));
+
+				var previous_color = canvas.buffer[x + canvas.width * y];
+				canvas.buffer[x + canvas.width * y] = previous_color.mix(&self.color, factor);
+
+				previous_color = canvas.buffer[x + canvas.width * (y - 1)];
+				canvas.buffer[x + canvas.width * (y - 1)] = self.color.mix(&previous_color, factor);
+
+				intersect_y += gradient;
+			}
+		}
+	}
+};