mask minifyBy2

src/pixie/masks.nim

@@ -63,5 +63,23 @@ proc `[]=`*(mask: Mask, x, y: int, value: uint8) {.inline.} =
   if mask.inside(x, y):
     mask.setValueUnsafe(x, y, value)
 
+proc minifyBy2*(mask: Mask, power = 1): Mask =
+  ## Scales the mask down by an integer scale.
+  if power < 0:
+    raise newException(PixieError, "Cannot minifyBy2 with negative power")
+  if power == 0:
+    return mask.copy()
+
+  for i in 1 .. power:
+    result = newMask(mask.width div 2, mask.height div 2)
+    for y in 0 ..< result.height:
+      for x in 0 ..< result.width:
+        let value =
+          mask.getValueUnsafe(x * 2 + 0, y * 2 + 0).uint32 +
+          mask.getValueUnsafe(x * 2 + 1, y * 2 + 0) +
+          mask.getValueUnsafe(x * 2 + 1, y * 2 + 1) +
+          mask.getValueUnsafe(x * 2 + 0, y * 2 + 1)
+        result.setValueUnsafe(x, y, (value div 4).uint8)
+
 when defined(release):
   {.pop.}

tests/test_masks.nim

@@ -0,0 +1,19 @@
+import pixie, pixie/fileformats/png
+
+block:
+  let
+    mask = newMask(100, 100)
+    r = 10.0
+    x = 10.0
+    y = 10.0
+    h = 80.0
+    w = 80.0
+  var path: Path
+  path.moveTo(x + r, y)
+  path.arcTo(x + w, y, x + w, y + h, r)
+  path.arcTo(x + w, y + h, x, y + h, r)
+  path.arcTo(x, y + h, x, y, r)
+  path.arcTo(x, y, x + w, y, r)
+  mask.fillPath(path)
+
+  writeFile("tests/images/masks/maskMinified.png", mask.minifyBy2().encodePng())