implement switching off anti-aliasing

Author: jonaspleyer

plotters-backend/src/rasterizer/circle.rs

@@ -100,22 +100,27 @@ fn draw_sweep_line<B: DrawingBackend, S: BackendStyle>(
     let vs = s.ceil() - s;
     let ve = e - e.floor();
 
+    let (s1, s2) = if b.use_anti_aliasing() {
+        (style.color().mix(vs), style.color().mix(ve))
+    } else {
+        (style.color(), style.color())
+    };
     if dx == 0 {
         check_result!(b.draw_line(
             (p0 + x0, s.ceil() as i32 + y0),
             (p0 + x0, e.floor() as i32 + y0),
             &style.color()
         ));
-        check_result!(b.draw_pixel((p0 + x0, s.ceil() as i32 + y0 - 1), style.color().mix(vs)));
-        check_result!(b.draw_pixel((p0 + x0, e.floor() as i32 + y0 + 1), style.color().mix(ve)));
+        check_result!(b.draw_pixel((p0 + x0, s.ceil() as i32 + y0 - 1), s1));
+        check_result!(b.draw_pixel((p0 + x0, e.floor() as i32 + y0 + 1), s2));
     } else {
         check_result!(b.draw_line(
             (s.ceil() as i32 + x0, p0 + y0),
             (e.floor() as i32 + x0, p0 + y0),
             &style.color()
         ));
-        check_result!(b.draw_pixel((s.ceil() as i32 + x0 - 1, p0 + y0), style.color().mix(vs)));
-        check_result!(b.draw_pixel((e.floor() as i32 + x0 + 1, p0 + y0), style.color().mix(ve)));
+        check_result!(b.draw_pixel((s.ceil() as i32 + x0 - 1, p0 + y0), s1));
+        check_result!(b.draw_pixel((e.floor() as i32 + x0 + 1, p0 + y0), s2));
     }
 
     Ok(())
@@ -319,22 +324,28 @@ pub fn draw_circle<B: DrawingBackend, S: BackendStyle>(
         let top = center.1 - lx.floor() as i32;
         let bottom = center.1 + lx.floor() as i32;
 
+        // Do not use flat color but interpolate when using anti-aliasing
+        let (s1, s2) = if b.use_anti_aliasing() {
+            (style.color().mix(1.0 - v), style.color().mix(v))
+        } else {
+            (style.color(), style.color())
+        };
         if fill {
             check_result!(b.draw_line((left, y), (right, y), &style.color()));
             check_result!(b.draw_line((x, top), (x, up - 1), &style.color()));
             check_result!(b.draw_line((x, down + 1), (x, bottom), &style.color()));
         } else {
-            check_result!(b.draw_pixel((left, y), style.color().mix(1.0 - v)));
-            check_result!(b.draw_pixel((right, y), style.color().mix(1.0 - v)));
+            check_result!(b.draw_pixel((left, y), s1));
+            check_result!(b.draw_pixel((right, y), s1));
 
-            check_result!(b.draw_pixel((x, top), style.color().mix(1.0 - v)));
-            check_result!(b.draw_pixel((x, bottom), style.color().mix(1.0 - v)));
+            check_result!(b.draw_pixel((x, top), s1));
+            check_result!(b.draw_pixel((x, bottom), s1));
         }
 
-        check_result!(b.draw_pixel((left - 1, y), style.color().mix(v)));
-        check_result!(b.draw_pixel((right + 1, y), style.color().mix(v)));
-        check_result!(b.draw_pixel((x, top - 1), style.color().mix(v)));
-        check_result!(b.draw_pixel((x, bottom + 1), style.color().mix(v)));
+        check_result!(b.draw_pixel((left - 1, y), s2));
+        check_result!(b.draw_pixel((right + 1, y), s2));
+        check_result!(b.draw_pixel((x, top - 1), s2));
+        check_result!(b.draw_pixel((x, bottom + 1), s2));
     }
 
     Ok(())

plotters-backend/src/rasterizer/line.rs

@@ -81,10 +81,16 @@ pub fn draw_line<DB: DrawingBackend, S: BackendStyle>(
     let grad = f64::from(to.1 - from.1) / f64::from(to.0 - from.0);
 
     let mut put_pixel = |(x, y): BackendCoord, b: f64| {
+        // Do not use flat color but interpolate when using anti-aliasing
+        let st = if back.use_anti_aliasing() {
+            style.color().mix(b)
+        } else {
+            style.color()
+        };
         if steep {
-            back.draw_pixel((y, x), style.color().mix(b))
+            back.draw_pixel((y, x), st)
         } else {
-            back.draw_pixel((x, y), style.color().mix(b))
+            back.draw_pixel((x, y), st)
         }
     };
 

plotters-backend/src/rasterizer/polygon.rs

@@ -200,34 +200,33 @@ pub fn fill_polygon<DB: DrawingBackend, S: BackendStyle>(
                             continue;
                         }
 
+                        let (mut s1, mut s2) = (style.color(), style.color());
                         if horizontal_sweep {
+                            // Do not use flat color but interpolate when using anti-aliasing
+                            if back.use_anti_aliasing() {
+                                s1 = style.color().mix(from.ceil() - from);
+                                s2 = style.color().mix(to - to.floor());
+                            }
                             check_result!(back.draw_line(
                                 (sweep_line, from.ceil() as i32),
                                 (sweep_line, to.floor() as i32),
                                 &style.color(),
                             ));
-                            check_result!(back.draw_pixel(
-                                (sweep_line, from.floor() as i32),
-                                style.color().mix(from.ceil() - from),
-                            ));
-                            check_result!(back.draw_pixel(
-                                (sweep_line, to.ceil() as i32),
-                                style.color().mix(to - to.floor()),
-                            ));
+                            check_result!(back.draw_pixel((sweep_line, from.floor() as i32), s1,));
+                            check_result!(back.draw_pixel((sweep_line, to.ceil() as i32), s2,));
                         } else {
+                            // Do not use flat color but interpolate when using anti-aliasing
+                            if back.use_anti_aliasing() {
+                                s1 = style.color().mix(from.ceil() - from);
+                                s2 = style.color().mix(to.floor() - to);
+                            }
                             check_result!(back.draw_line(
                                 (from.ceil() as i32, sweep_line),
                                 (to.floor() as i32, sweep_line),
                                 &style.color(),
                             ));
-                            check_result!(back.draw_pixel(
-                                (from.floor() as i32, sweep_line),
-                                style.color().mix(from.ceil() - from),
-                            ));
-                            check_result!(back.draw_pixel(
-                                (to.ceil() as i32, sweep_line),
-                                style.color().mix(to.floor() - to),
-                            ));
+                            check_result!(back.draw_pixel((from.floor() as i32, sweep_line), s1,));
+                            check_result!(back.draw_pixel((to.ceil() as i32, sweep_line), s2,));
                         }
 
                         first = None;