Round down colors evenly in reduce_color()

WonderfulToolchain · Dec 16, 2024 · b1645a4 · b1645a4
1 parent cbef58a
commit b1645a4
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Showing 2 changed files with 17 additions and 12 deletions.
diff --git a/src/Color.h b/src/Color.h
@@ -73,6 +73,11 @@ constexpr channel_t scale_up(channel_t value, unsigned shift) {
   }
 }
 
+// scale down value, rounding evenly
+constexpr channel_t scale_down(channel_t value, unsigned shift) {
+  return (value + (1 << (shift - 1))) >> shift;
+}
+
 //
 // rgba_color / hsva_color
 //

diff --git a/src/Mode.h b/src/Mode.h
@@ -334,9 +334,9 @@ inline rgba_t reduce_color(const rgba_t color, Mode to_mode) {
       return transparent_color;
     } else {
       rgba_color c(color);
-      c.r >>= 3;
-      c.g >>= 3;
-      c.b >>= 3;
+      c.r = scale_down(c.r, 3);
+      c.g = scale_down(c.g, 3);
+      c.b = scale_down(c.b, 3);
       rgba_t scaled = c;
       return (scaled & 0x00ffffff) + 0xff000000;
     }
@@ -372,18 +372,18 @@ inline rgba_t reduce_color(const rgba_t color, Mode to_mode) {
       return transparent_color;
     } else {
       rgba_color c(color);
-      c.r >>= 5;
-      c.g >>= 5;
-      c.b >>= 5;
+      c.r = scale_down(c.r, 5);
+      c.g = scale_down(c.g, 5);
+      c.b = scale_down(c.b, 5);
       rgba_t scaled = c;
       return (scaled & 0x00ffffff) + 0xff000000;
     }
     break;
   case Mode::sms: {
     rgba_color c(color);
-    c.r >>= 6;
-    c.g >>= 6;
-    c.b >>= 6;
+    c.r = scale_down(c.r, 6);
+    c.g = scale_down(c.g, 6);
+    c.b = scale_down(c.b, 6);
     rgba_t scaled = c;
     return (scaled & 0x00ffffff) + 0xff000000;
   }
@@ -395,9 +395,9 @@ inline rgba_t reduce_color(const rgba_t color, Mode to_mode) {
       return transparent_color;
     } else {
       rgba_color c(color);
-      c.r >>= 4;
-      c.g >>= 4;
-      c.b >>= 4;
+      c.r = scale_down(c.r, 4);
+      c.g = scale_down(c.g, 4);
+      c.b = scale_down(c.b, 4);
       rgba_t scaled = c;
       return (scaled & 0x00ffffff) + 0xff000000;
     }